# Publications

### Under review

1. M. Tahmasbi and M. R. Bloch, “Covert Secret Key Generation with an Active Warden.” submitted to IEEE Transactions on Information Forensics and Security, Jan. 2019.

We investigate the problem of covert and secret key generation over a discrete memoryless channel model with one way public discussion and in presence of an active warden who can arbitrarily vary its channel and tamper with the main channel when an information symbol is sent. In this scenario, we develop an adaptive protocol that is required to conceal not only the key but also whether a protocol is being implemented. Based on the adversary’s actions, this protocol generates a key whose size depends on the adversary’s actions. Moreover, for a passive adversary and for some models that we identify, we show that covert secret key generation is possible and characterize the covert secret key capacity in special cases; in particular, the covert secret key capacity is sometimes equal to the covert capacity of the channel, so that secrecy comes “for free."

@misc{Tahmasbi2019,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R},
title = {Covert Secret Key Generation with an Active Warden},
howpublished = {submitted to \emph{IEEE Transactions on Information Forensics and Security}},
month = jan,
year = {2019},
eprint = {1901.02044},
groups = {Steganography and covert communications}
}


2. M. Le Treust and M. R. Bloch, “State Leakage and Coordination of Actions: Core of the Receiver’s Knowledge.” submitted to IEEE Transactions on Information Theory, Dec. 2018.

We revisit the problems of state masking and state amplification through the lens of empirical coordination by considering a state-dependent channel in which the encoder has causal and strictly causal state knowledge. We show that the problem of empirical coordination provides a natural framework in which to jointly study the problems of reliable communication, state masking, and state amplification. We characterize the regions of rate-equivocation-coordination trade-offs for several channel models with causal and strictly causal state knowledge. We introduce the notion of “core of the receiver’s knowledge” to capture what the decoder can infer about all the signals involved in the model. We exploit this result to solve a channel state estimation zero-sum game in which the encoder prevents the decoder to estimate the channel state accurately.

@misc{LeTreust2018,
author = {{Le Treust}, Ma\"el and Bloch, Matthieu R},
title = {State Leakage and Coordination of Actions: Core of the Receiver's Knowledge},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = dec,
year = {2018},
eprint = {1812.07026}
}


3. H. Zivari-Fard, M. Bloch, and A. Nosratinia, “Secrecy Rates for a Channel With Two Senders and Two Receivers.” submitted to IEEE Transactions on Information Theory, Dec. 2018.

@misc{Zivari-Fard2018,
author = {Zivari-Fard, Hassan and Bloch, Matthieu and Nosratinia, Aria},
title = {Secrecy Rates for a Channel With Two Senders and Two Receivers},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = dec,
year = {2018}
}


4. I. A. Kadampot, M. Tahmasbi, and M. R. Bloch, “Multilevel-Coded Pulse-Position Modulation for Covert Communications over Binary-Input Discrete Memoryless Channels.” submitted to IEEE Transactions on Information Theory, Nov. 2018.

We develop a low-complexity coding scheme to achieve covert communications over binary-input discrete memoryless channels (BI-DMCs). We circumvent the impossibility of covert communication with linear codes by introducing non-linearity through the use of pulse position modulation (PPM) and multilevel coding (MLC). We show that the MLC-PPM scheme exhibits many appealing properties; in particular, the channel at a given index level remains stationary as the number of level increases, which allows one to use families of channel capacity- and channel resolvability-achieving codes to concretely instantiate the covert communication scheme.

@misc{Kadampot2018a,
author = {Kadampot, Ishaque Ashar and Tahmasbi, Mehrdad and Bloch, Matthieu R},
title = {Multilevel-Coded Pulse-Position Modulation for Covert Communications over Binary-Input Discrete Memoryless Channels},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = nov,
year = {2018},
eprint = {1811.09695}
}


5. M. Tahmasbi and M. R. Bloch, “A framework for covert and secret key expansion over quantum channels.” submitted to Physical Review A, Nov. 2018.

Covert and secret quantum key distribution aims at generating information-theoretically secret bits between distant legitimate parties in a manner that remains provably undetectable by an adversary. We propose a framework in which to precisely define and analyze such an operation, and we show that covert and secret key expansion is possible. For fixed and known classical-quantum channels, we develop and analyze protocols based on forward and reverse reconciliation. When the adversary applies the same quantum channel independently on each transmitted quantum state, akin to a collective attack in the quantum key distribution literature, we propose a protocol that achieves covert and secret key expansion under mild restrictions. The crux of our approach is the use of information reconciliation and privacy amplification techniques that are able to process the sparse signals required for covert operation and whose Shannon entropy scales as the square root of their length. In particular, our results show that the coordination required between legitimate parties to achieve covert communication can be achieved with a negligible number of secret key bits.

@misc{Tahmasbi2018b,
author = {Tahmasbi, Merhdad and Bloch, Matthieu R},
title = {A framework for covert and secret key expansion over quantum channels},
howpublished = {submitted to Physical Review A},
month = nov,
year = {2018},
eprint = {1811.05626},
groups = {Quantum key distribution}
}


6. N. Helhal, M. Bloch, and A. Nosratinia, “Cooperative Resolvability and Secrecy in the Cribbing Multiple-Access Channel.” submitted for IEEE Transactions on Information Theory, Nov. 2018.

We study channel resolvability for the discrete memoryless multiple-access channel with cribbing, i.e., the characterization of the amount of randomness required at the inputs to approximately produce a chosen i.i.d. output distribution according to Kullback-Leibler divergence. We analyze resolvability rates when one encoder cribs (i) the input of the other encoder; or the output of the other encoder, (ii) non-causally, (iii) causally, or (iv) strictly-causally. For scenarios (i)-(iii), we exactly characterize the channel resolvability region. For (iv), we provide inner and outer bounds for the channel resolvability region; the crux of our achievability result is to handle the strict causality constraint with a block-Markov coding scheme in which dependencies across blocks are suitably hidden. Finally, we leverage the channel resolvability results to derive achievable secrecy rate regions for each of the cribbing scenarios under strong secrecy constraints.

@misc{Helhal2018a,
author = {Helhal, Noha and Bloch, Matthieu and Nosratinia, Aria},
title = {Cooperative Resolvability and Secrecy in the Cribbing Multiple-Access Channel},
howpublished = {submitted for \emph{IEEE Transactions on Information Theory}},
month = nov,
year = {2018},
eprint = {1811.11649}
}


7. M. Tahmasbi, A. Savard, and M. R. Bloch, “Covert Capacity of Non-Coherent Rayleigh-Fading Channels.” submitted to IEEE Transactions on Information Theory, Oct. 2018.

The covert capacity is characterized for a non-coherent fast Rayleigh-fading wireless channel, in which a legitimate user wishes to communicate reliably with a legitimate receiver while escaping detection from a warden. It is shown that the covert capacity is achieved with an amplitude-constrained input distribution that consists of a finite number of mass points including one at zero and numerically tractable bounds are provided. It is also conjectured that distributions with two mass points in fixed locations are optimal.

@misc{Tahmasbi2018a,
author = {Tahmasbi, Mehrdad and Savard, Anne and Bloch, Matthieu R},
title = {Covert Capacity of Non-Coherent Rayleigh-Fading Channels},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = oct,
year = {2018},
eprint = {1810.07687},
groups = {Steganography and covert communications}
}


8. K. S. K. Arumugam and M. R. Bloch, “Embedding Covert Information in Broadcast Communications.” submitted to IEEE Transactions on Information Forensics and Security, Aug. 2018.

We analyze a two-receiver binary-input discrete memoryless broadcast channel, in which the transmitter communicates a common message simultaneously to both receivers and a covert message to only one of them. The unintended recipient of the covert message is treated as an adversary who attempts to detect the covert transmission. This model captures the problem of embedding covert messages in an innocent codebook and generalizes previous covert communication models in which the innocent behavior corresponds to the absence of communication between legitimate users. We identify the exact asymptotic behavior of the number of covert bits that can be transmitted when the rate of the innocent codebook is close to the capacity of the channel to the adversary. Our results also identify the dependence of the number of covert bits on the channel parameters and the characteristics of the innocent codebook.

@misc{Arumugam2018b,
author = {Arumugam, Keerthi Suria Kumar and Bloch, Matthieu R.},
title = {Embedding Covert Information in Broadcast Communications},
howpublished = {submitted to \emph{IEEE Transactions on Information Forensics and Security}},
month = aug,
year = {2018},
eprint = {1808.09556},
groups = {Steganography and covert communications}
}


9. M. Tahmasbi, M. R. Bloch, and A. Yener, “Learning an Adversary’s Actions for Secret Communication.” submitted to IEEE Transactions on Information Theory, Jul. 2018.

@misc{Tahmasbi2018,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R. and Yener, Aylin},
title = {Learning an Adversary's Actions for Secret Communication},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = jul,
year = {2018},
eprint = {1807.08670}
}


10. R. Chou, M. Bloch, and A. Yener, “Universal Covertness for Discrete Memoryless Sources.” submitted to IEEE Transactions on Information Theory, Jul. 2018.

Consider a sequence Xn of length n emitted by a Discrete Memoryless Source (DMS) with unknown distribution pX. The objective is to construct a lossless source code that maps Xn to a sequence Yˆm of length m that is indistinguishable, in terms of Kullback-Leibler divergence, from a sequence emitted by another DMS with known distribution pY. The main result is the existence of a coding scheme that performs this task with an optimal ratio m/n equal to H(X)/H(Y), the ratio of the Shannon entropies of the two distributions, as n goes to infinity. The coding scheme overcomes the challenges created by the lack of knowledge about pX by relying on a sufficiently fine estimation of H(X), followed by an appropriately designed type-based source coding that jointly performs source resolvability and universal lossless source coding. The result recovers and extends previous results that either assume pX or pY uniform, or pX known. The price paid for these generalizations is the use of common randomness with vanishing rate, whose length roughly scales as the square root of n. By allowing common randomness strictly larger than the square root of n but still negligible compared to n, a constructive low-complexity encoding and decoding counterpart to the main result is also provided for binary sources by means of polar codes.

@misc{Chou2018,
author = {Chou, R\'emi and Bloch, Matthieu and Yener, Aylin},
title = {Universal Covertness for Discrete Memoryless Sources},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = jul,
year = {2018},
eprint = {1808.05612}
}


11. K. S. K. Arumugam and M. R. Bloch, “Covert Communication over a K-user Multiple-Access Channel.” submitted to IEEE Transactions on Information Theory, Mar. 2018.

We consider a scenario in which K transmitters attempt to communicate covert messages reliably to a legitimate receiver over a discrete memoryless multiple-access channel (MAC) while simultaneously escaping detection from an adversary who observes their communication through another discrete memoryless MAC. We assume that each transmitter may use a secret key that is shared only between itself and the legitimate receiver. We show that each of the K transmitters can transmit on the order of n‾√ reliable and covert bits per n channel uses, exceeding which, the warden will be able to detect the communication. We identify the optimal pre-constants of the scaling, which leads to a complete characterization of the covert capacity region of the K-user binary-input MAC. We show that, asymptotically, all sum-rate constraints are inactive unlike the traditional MAC capacity region. We also characterize the channel conditions that have to be satisfied for the transmitters to operate without a secret key.

@misc{Arumugam2018a,
author = {Arumugam, Keerthi Suria Kumar and Bloch, Matthieu R.},
title = {Covert Communication over a {K}-user Multiple-Access Channel},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = mar,
year = {2018},
eprint = {1803.06007},
groups = {Steganography and covert communications}
}


12. G. Cervia, L. Luzzi, M. Le Treust, and M. Bloch, “Strong Coordination of Signals and Actions over Noisy Channels with two-sided State Information.” submitted to IEEE Transactions on Information Theory, Mar. 2018.

We consider a network of two nodes separated by a noisy channel with two-sided state information, in which the input and output signals have to be coordinated with the source and its reconstruction. In the case of non-causal encoding and decoding, we propose a joint source-channel coding scheme and develop inner and outer bounds for the strong coordination region. While the inner and outer bounds do not match in general, we provide a complete characterization of the strong coordination region in three particular cases: i) when the channel is perfect; ii) when the decoder is lossless; and iii) when the random variables of the channel are independent from the random variables of the source. Through the study of these special cases, we prove that the separation principle does not hold for joint source-channel strong coordination. Finally, in the absence of state information, we show that polar codes achieve the best known inner bound for the strong coordination region, which therefore offers a constructive alternative to random binning and coding proofs.

@misc{Cervia2018,
author = {Cervia, Giulia and Luzzi, Laura and {Le Treust}, Ma\"el and Bloch, Matthieu},
title = {Strong Coordination of Signals and Actions over Noisy Channels with two-sided State Information},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = mar,
year = {2018},
eprint = {1801.10543}
}


13. S. Salimi, M. Bloch, F. Gabry, M. Skoglund, and P. Papadimitratos, “Strong Secrecy in Pairwise Key Agreement over a Generalized Multiple Access Channel.” submitted to IEEE Transactions on Information Theory, Mar. 2016.

@misc{Salimi2016,
author = {Salimi, Somayeh and Bloch, Matthieu and Gabry, Fr\'ed\'eric and Skoglund, Mikael and Papadimitratos, Panagiotis},
title = {Strong Secrecy in Pairwise Key Agreement over a Generalized Multiple Access Channel},
howpublished = {submitted to \emph{IEEE Transactions on Information Theory}},
month = mar,
year = {2016},
eprint = {1603.05399},
groups = {Secret key agreement},
owner = {mattbloch},
timestamp = {2016.03.15}
}


14. A. J. Pierrot, R. A. Chou, and M. R. Bloch, “The Effect of Eavesdropper’s Statistics in Experimental Wireless Secret-Key Generation.” submitted to IEEE Transactions on Information Forensics and Security, Jun. 2014.

@misc{Pierrot2013c,
author = {Pierrot, Alexandre J. and Chou, Remi A. and Bloch, Matthieu R.},
title = {The Effect of Eavesdropper's Statistics in Experimental Wireless Secret-Key Generation},
howpublished = {submitted to \emph{IEEE Transactions on Information Forensics and Security}},
month = jun,
year = {2014},
eprint = {1312.3304},
groups = {Experimental systems},
owner = {mattbloch},
timestamp = {2013.12.11}
}


### Accepted

1. M. Tahmasbi and M. R. Bloch, “First and Second Order Asymptotics in Covert Communication.” accepted to IEEE Transactions on Information Theory, Oct. 2018.

We study the first- and second-order asymptotics of covert communication over binary-input DMC for three different covertness metrics and under maximum probability of error constraint. When covertness is measured in terms of the relative entropy between the channel output distributions induced with and without communication, we characterize the exact first- and second-order asymptotics of the number of bits that can be reliably transmitted with a maximum probability of error less than εand a relative entropy less than δ. When covertness is measured in terms of the variational distance between the channel output distributions or in terms of the probability of missed detection for fixed probability of false alarm, we establish the exact first-order asymptotics and bound the second-order asymptotics. PPM achieves the optimal first-order asymptotics for all three metrics, as well as the optimal second-order asymptotics for relative entropy. The main conceptual contribution of this paper is to clarify how the choice of a covertness metric impacts the information-theoretic limits of covert communications. The main technical contribution underlying our results is a detailed expurgation argument to show the existence of a code satisfying the reliability and covertness criteria.

@misc{Tahmasbi2017,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R},
title = {First and Second Order Asymptotics in Covert Communication},
howpublished = {accepted to \emph{IEEE Transactions on Information Theory}},
month = oct,
year = {2018},
doi = {10.1109/TIT.2018.2878526},
eprint = {1703.01362},
groups = {Steganography and covert communications}
}


2. G. Cervia, L. Luzzi, M. Le Treust, and M. R. Bloch, “Strong coordination over noisy channels with strictly causal encoding.” accepted to Allerton Conference on Communication, Control, and Computing, Aug. 2018.

We consider a network of two nodes separated by a noisy channel, in which the input and output signals have to be coordinated with the source and its reconstruction. In the case of strictly causal encoding and non-causal decoding, we prove inner and outer bounds for the strong coordination region and show that the inner bound is achievable with polar codes.

@misc{Cervia2018a,
author = {Cervia, Giulia and Luzzi, Laura and {Le Treust}, Mael and Bloch, Matthieu R},
title = {Strong coordination over noisy channels with strictly causal encoding},
howpublished = {accepted to \emph{Allerton Conference on Communication, Control, and Computing}},
month = aug,
year = {2018},
eprint = {1809.10934},
groups = {Coordination of networks}
}


3. W. K. Harrison and M. R. Bloch, “On Dual Relationships of Secrecy Codes.” accepted to Allerton Conference on Communication, Control, and Computing, Aug. 2018.

We investigate properties of finite blocklength codes and their duals when used for coset coding over the binary era- sure wiretap channel (BEWC). We identify sufficient conditions, related to the ranks of sub-matrices of a generator matrix that codes may satisfy to achieve the maximum equivocation among all codes with given blocklength and dimension, irrespective of the eavesdropper’s channel erasure probability. We point out that binary maximum distance separable (MDS) codes are optimal for secrecy and we also show that simplex codes (and Hamming codes) have higher equivocation than families of codes with a single repeated column in the generator matrix (parity-check matrix). We conjecture that simplex and Hamming codes are optimal when used as the base linear code in a coset coding scheme for secrecy over the BEWC.

@misc{Harrison2018,
author = {Harrison, Willie K. and Bloch, Matthieu R.},
title = {On Dual Relationships of Secrecy Codes},
howpublished = {accepted to \emph{Allerton Conference on Communication, Control, and Computing}},
month = aug,
year = {2018},
groups = {Wiretap codes}
}


### Articles

1. R. A. Chou, M. R. Bloch, and J. Kliewer, “Empirical and Strong Coordination via Soft Covering with Polar Codes,” IEEE Transactions on Information Theory, vol. 64, no. 7, pp. 5087–5100, Jul. 2018.

We design polar codes for empirical coordination and strong coordination in two-node networks. Our constructions hinge on the fact that polar codes enable explicit low-complexity schemes for soft covering. We leverage this property to propose explicit and low-complexity coding schemes that achieve the capacity regions of both empirical coordination and strong coordination for sequences of actions taking value in an alphabet of prime cardinality. Our results improve previously known polar coding schemes, which (i) were restricted to uniform distributions and to actions obtained via binary symmetric channels for strong coordination, (ii) required a non-negligible amount of common randomness for empirical coordination, and (iii) assumed that the simulation of discrete memoryless channels could be perfectly implemented. As a by-product of our results, we obtain a polar coding scheme that achieves channel resolvability for an arbitrary discrete memoryless channel whose input alphabet has prime cardinality.

@article{Chou2016a,
author = {Chou, Remi A. and Bloch, Matthieu R. and Kliewer, Joerg},
title = {Empirical and Strong Coordination via Soft Covering with Polar Codes},
journal = {IEEE Transactions on Information Theory},
year = {2018},
volume = {64},
number = {7},
pages = {5087-5100},
month = jul,
issn = {0018-9448},
doi = {10.1109/TIT.2018.2817519},
eprint = {1608.08474},
groups = {Coordination of networks, Polar codes},
howpublished = {accepted to \emph{IEEE Transactions on Information Theory}}
}


2. B. Larrousse, S. Lasaulce, and M. Bloch, “Coordination in distributed networks via coded actions with application to power control,” IEEE Transactions on Information Theory, vol. 64, no. 5, pp. 3633–3654, May 2018.

This paper investigates the problem of coordinating several agents through their actions. Although the methodology applies to general scenarios, the present work focuses on a situation with an asymmetric observation structure that only involves two agents. More precisely, one of the agents knows the past, present, and future realizations of a state (the system state) that affects the common payoff function of the agents; in contrast, the second agent is assumed either to know the past realizations of the system state or to have no knowledge of it. In both cases, the second agent has access to some strictly causal observations of the first agent’s actions, which enables the two agents to coordinate. These scenarios are applied to the problem of distributed power control; the key idea is that a transmitter may embed information about the wireless channel state into its transmit power levels so that an observation of these levels, e.g. the signal-to-interference plus noise ratio, allows the other transmitter to coordinate its power levels. The main contributions of this paper are twofold. First, we provide a characterization of the set of feasible average payoffs when the agents repeatedly take long sequences of actions and the realizations of the system state are \acsiid. Second, we exploit these results in the context of distributed power control and introduce the concept of coded power control. We carry out an extensive numerical analysis of the benefits of coded power control over alternative power control policies, and highlight a simple yet non-trivial example of a power control code.

@article{Larrousse2014,
author = {Larrousse, Benjamin and Lasaulce, Samson and Bloch, Matthieu},
title = {Coordination in distributed networks via coded actions with application to power control},
journal = {IEEE Transactions on Information Theory},
year = {2018},
volume = {64},
number = {5},
pages = {3633--3654},
month = may,
doi = {10.1109/TIT.2018.2809008},
eprint = {1501.03685},
howpublished = {accepted in \emph{IEEE Transactions on Information Theory}},
owner = {mattbloch},
timestamp = {2014.10.31}
}


3. B. N. Vellambi, J. Kliewer, and M. R. Bloch, “Strong Coordination Over Multi-Hop Line Networks Using Channel Resolvability Codebooks,” IEEE Transactions on Information Theory, vol. 64, no. 2, pp. 1132–1162, Feb. 2018.

We analyze the problem of strong coordination over a multi-hop line network in which the node initiating the coordination is a terminal network node. We assume that each node has access to a certain amount of randomness that is local to the node, and that the nodes also have shared common randomness, which are used together with explicit hop-by-hop communication to achieve information-theoretic strong coordination. We derive the trade-offs among the required rates of communication on the network links, the rates of local randomness available at network nodes, and the rate of common randomness to realize strong coordination. We present an achievable coding scheme built using multiple layers of channel resolvability codes, and establish several settings in which this scheme offers the best possible trade-offs among network resources.

@article{Vellambi2016a,
author = {Vellambi, Badri N. and Kliewer, Joerg and Bloch, Matthieu R},
title = {Strong Coordination Over Multi-Hop Line Networks Using Channel Resolvability Codebooks},
journal = {IEEE Transactions on Information Theory},
year = {2018},
volume = {64},
number = {2},
pages = {1132-1162},
month = feb,
issn = {0018-9448},
doi = {10.1109/TIT.2017.2768529},
eprint = {1602.09001},
groups = {Coordination of networks},
keywords = {Communication system signaling;Encoding;Indexes;Random variables;Robot kinematics;Spread spectrum communication;Strong coordination;channel resolvability;channel synthesis;line network},
owner = {mattbloch},
timestamp = {2016.04.09}
}


4. G. Frèche, M. Bloch, and M. Barret, “Polar Codes for Covert Communications over Asynchronous Discrete Memoryless Channels,” Entropy, vol. 20, no. 1, p. 3, Dec. 2017.

This paper introduces an explicit covert communication code for binary-input asynchronous discrete memoryless channels based on binary polar codes, in which legitimate parties exploit uncertainty created by both the channel noise and the time of transmission to avoid detection by an adversary. The proposed code jointly ensures reliable communication for a legitimate receiver and low probability of detection with respect to the adversary, both observing noisy versions of the codewords. Binary polar codes are used to shape the weight distribution of codewords and ensure that the average weight decays as the block length grows. The performance of the proposed code is severely limited by the speed of polarization, which in turn controls the decay of the average codeword weight with the block length. Although the proposed construction falls largely short of achieving the performance of random codes, it inherits the low-complexity properties of polar codes.

@article{Freche2017,
author = {Fr\eche, Guillaume and Bloch, Matthieu and Barret, Michel},
title = {Polar Codes for Covert Communications over Asynchronous Discrete Memoryless Channels},
journal = {Entropy},
year = {2017},
volume = {20},
number = {1},
pages = {3},
month = dec,
issn = {1099-4300},
doi = {10.3390/e20010003},
file = {:2017-Freche-Entropy.pdf:PDF},
groups = {Steganography and covert communications, Polar codes}
}


5. R. A. Chou, B. N. Vellambi, M. R. Bloch, and J. Kliewer, “Coding Schemes for Achieving Strong Secrecy at Negligible Cost,” IEEE Transactions on Information Theory, vol. 63, no. 3, pp. 1858–1873, Mar. 2017.

We study the problem of achieving strong secrecy over wiretap channels at negligible cost, in the sense of maintaining the overall communication rate of the same channel without secrecy constraints. Specifically, we propose and analyze two source-channel coding architectures, in which secrecy is achieved by multiplexing public and confidential messages. In both cases, our main contribution is to show that secrecy can be achieved without compromising communication rate and by requiring only randomness of asymptotically vanishing rate. Our first source-channel coding architecture relies on a modified wiretap channel code, in which randomization is performed using the output of a source code. In contrast, our second architecture relies on a standard wiretap code combined with a modified source code termed uniform compression code, in which a small shared secret seed is used to enhance the uniformity of the source code output. We carry out a detailed analysis of uniform compression codes and characterize the optimal size of the shared seed.

@article{Chou2014b,
author = {Chou, R. A. and Vellambi, B. N. and Bloch, M. R. and Kliewer, J.},
title = {Coding Schemes for Achieving Strong Secrecy at Negligible Cost},
journal = {IEEE Transactions on Information Theory},
year = {2017},
volume = {63},
number = {3},
pages = {1858-1873},
month = mar,
issn = {0018-9448},
doi = {10.1109/TIT.2016.2645225},
eprint = {1508.07920},
groups = {Wiretap channels},
keywords = {channel coding;cryptography;message authentication;multiplexing;source coding;telecommunication security;asymptotically vanishing rate randomness;confidential messages;modified source code;modified wiretap channel code;multiplexing;optimal size characterization;public messages;shared secret seed;source code output uniformity enhancement;source-channel coding architectures;strong secrecy problem;uniform compression code;Channel models;Decoding;Encoding;Multiplexing;Physical layer;Security;Virtual private networks;Wiretap channel;multiplexing;physical-layer security;source coding},
owner = {mattbloch},
timestamp = {2014.06.15}
}


6. R. A. Chou and M. R. Bloch, “Polar Coding for the Broadcast Channel with Confidential Messages: A Random Binning Analogy,” IEEE Transactions on Information Theory, vol. 62, no. 5, pp. 2410–2429, May 2016.

We develop a low-complexity polar coding scheme for the discrete memoryless broadcast channel with confidential messages under strong secrecy and randomness constraints. Our scheme extends previous work by using an optimal rate of uniform randomness in the stochastic encoder, and avoiding assumptions regarding the symmetry or degraded nature of the channels. The price paid for these extensions is that the encoder and the decoders are required to share a secret seed of negligible size and to increase the block length through chaining. We also highlight a close conceptual connection between the proposed polar coding scheme and a random binning proof of the secrecy capacity region.

@article{Chou2014d,
author = {Chou, Remi A. and Bloch, Matthieu R},
title = {Polar Coding for the Broadcast Channel with Confidential Messages: A Random Binning Analogy},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2016},
volume = {62},
number = {5},
pages = {2410-2429},
month = may,
issn = {0018-9448},
doi = {10.1109/TIT.2016.2539145},
eprint = {1411.0281},
groups = {Polar codes, Wiretap codes},
keywords = {Channel models;Decoding;Degradation;Encoding;Random variables;Security;Stochastic processes;Polar codes;physical-layer security;random binning;strong secrecy;wiretap channel},
owner = {mattbloch},
timestamp = {2014.10.31}
}


7. M. R. Bloch, “Covert Communication over Noisy Channels: A Resolvability Perspective,” IEEE Transactions on Information Theory, vol. 62, no. 5, pp. 2334–2354, May 2016.

We consider the situation in which a transmitter attempts to communicate reliably over a discrete memoryless channel, while simultaneously ensuring covertness (low probability of detection) with respect to a warden, who observes the signals through another discrete memoryless channel. We develop a coding scheme based on the principle of channel resolvability, which generalizes and extends prior work in several directions. First, it shows that irrespective of the quality of the channels, it is possible to communicate on the order of \sqrt n reliable and covert bits over n channel uses if the transmitter and the receiver share on the order of \sqrt n key bits. This improves upon earlier results requiring on the order of \sqrt n\log n key bits. Second, it proves that if the receiver’s channel is better than the warden’s channel in a sense that we make precise, it is possible to communicate on the order of \sqrt n reliable and covert bits over n channel uses without a secret key. This generalizes earlier results established for binary symmetric channels. We also identify the fundamental limits of covert and secret communications in terms of the optimal asymptotic scaling of the message size and key size, and we extend the analysis to Gaussian channels. The main technical problem that we address is how to develop concentration inequalities for low-weight sequences. The crux of our approach is to define suitably modified typical sets that are amenable to concentration inequalities.t

@article{Bloch2015b,
author = {Bloch, Matthieu R.},
title = {Covert Communication over Noisy Channels: A Resolvability Perspective},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2016},
volume = {62},
number = {5},
pages = {2334-2354},
month = may,
issn = {0018-9448},
doi = {10.1109/TIT.2016.2530089},
eprint = {1503.08778},
groups = {Steganography and covert communications},
keywords = {AWGN channels;Encoding;Memoryless systems;Noise measurement;Reliability theory;Covert communications;Shannon theory;low probability of detection;physical-layer security},
owner = {mattbloch},
timestamp = {2015.03.31}
}


8. R. A. Chou, M. R. Bloch, and E. Abbe, “Polar Coding for Secret-Key Generation,” IEEE Transactions on Information Theory, vol. 61, no. 11, pp. 6213–6237, Nov. 2015.

Practical implementations of secret-key generation are often based on sequential strategies, which handle reliability and secrecy in two successive steps, called reconciliation and privacy amplification. In this paper, we propose an alternative approach based on polar codes that jointly deals with reliability and secrecy. Specifically, we propose secret-key capacityachieving polar coding schemes for the following models: (i) the degraded binary memoryless source (DBMS) model with rateunlimited public communication, (ii) the DBMS model with oneway rate-limited public communication, (iii) the 1-to-m broadcast model and (iv) the Markov tree model with uniform marginals. For models (i) and (ii) our coding schemes remain valid for nondegraded sources, although they may not achieve the secret-key capacity. For models (i), (ii) and (iii), our schemes rely on preshared secret seed of negligible rate; however, we provide special cases of these models for which no seed is required. Finally, we show an application of our results to secrecy and privacy for biometric systems. We thus provide the first examples of lowcomplexity secret-key capacity-achieving schemes that are able to handle vector quantization for model (ii), or multiterminal communication for models (iii) and (iv).

@article{Chou2013b,
author = {Chou, Remi A. and Bloch, Matthieu R and Abbe, Emmanuel},
title = {Polar Coding for Secret-Key Generation},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2015},
volume = {61},
number = {11},
pages = {6213-6237},
month = nov,
issn = {0018-9448},
doi = {10.1109/TIT.2015.2471179},
eprint = {1305.4746},
groups = {Secret key agreement, Polar codes},
keywords = {Biological system modeling;Decoding;Encoding;Markov processes;Privacy;Protocols;Reliability},
owner = {mattbloch},
timestamp = {2013.10.09}
}


9. M. R. Bloch, M. Hayashi, and A. Thangaraj, “Error-Control Coding for Physical-Layer Secrecy,” Proceedings of IEEE, vol. 103, no. 10, pp. 1725–1746, Oct. 2015.

The renewed interest for physical-layer security techniques has put forward a new role for error-control codes. In addition to ensuring reliability, carefully designed codes have been shown to provide a level of information-theoretic secrecy, by which the amount of information leaked to an adversary may be controlled. The ability to achieve information-theoretic secrecy relies on the study of alternative coding mechanisms, such as channel resolvability and privacy amplification, in which error-control codes are exploited as a means to shape the distribution of stochastic processes. This use of error-control codes, which goes much beyond that of correcting errors, creates numerous new design challenges. The objective of this paper is threefold. First, the paper aims at providing system engineers with explicit tools to build simple secrecy codes in order to stimulate interest and foster their integration in communication system prototypes. Second, it aims at providing coding and information theorists with a synthetic overview of the theoretical concepts and techniques for secrecy. Finally, it aims at highlighting the open challenges and opportunities faced for the integration of these codes in practical systems.

@article{Bloch2015a,
author = {Bloch, Matthieu R and Hayashi, Masahito and Thangaraj, Andrew},
title = {Error-Control Coding for Physical-Layer Secrecy},
journal = {{P}roceedings of {IEEE}},
year = {2015},
volume = {103},
number = {10},
pages = {1725-1746},
month = oct,
issn = {0018-9219},
doi = {10.1109/JPROC.2015.2463678},
groups = {Wiretap codes},
keywords = {Channel coding;Communication system security;Cryptography;Decoding;Error analysis;Physical layer;Security;Semantics;Telecommunication services;Channel resolvability;error-control coding;physical-layer security;privacy amplification},
owner = {mattbloch},
timestamp = {2015.01.27}
}


10. V. Y. F. Tan and M. R. Bloch, “Information Spectrum Approach to Strong Converse Theorems for Degraded Wiretap Channels,” IEEE Transactions on Information Forensics and Security, vol. 10, no. 9, pp. 1891–1904, Sep. 2015.

We consider block codes for degraded wiretap channels in which the legitimate receiver decodes the message with an asymptotic error probability no larger than epsilon but the leakage to the eavesdropper vanishes. For discrete memoryless and Gaussian wiretap channels, we show that the maximum rate of transmission does not depend on epsilon in [0, 1), i.e., such channels possess the partial strong converse property. Furthermore, we derive sufficient conditions for the partial strong converse property to hold for memoryless but nonstationary symmetric and degraded wiretap channels. Our proof techniques leverage the information spectrum method, which allows us to establish a necessary and sufficient condition for the partial strong converse to hold for general wiretap channels without any information stability assumptions.

@article{Tan2014a,
author = {Tan, V.Y.F. and Bloch, M.R.},
title = {Information Spectrum Approach to Strong Converse Theorems for Degraded Wiretap Channels},
journal = {{IEEE} {T}ransactions on {I}nformation {F}orensics and {S}ecurity},
year = {2015},
volume = {10},
number = {9},
pages = {1891-1904},
month = sep,
issn = {1556-6013},
doi = {10.1109/TIFS.2015.2434592},
eprint = {1406.6758},
groups = {Wiretap channels},
keywords = {Gaussian channels;block codes;error statistics;telecommunication security;wireless channels;Gaussian wiretap channels;asymptotic error probability;block codes;degraded wiretap channels;discrete memoryless wiretap channels;eavesdropper;information spectrum method;legitimate receiver;partial strong converse property;Error probability;Manganese;Measurement;Mutual information;Random variables;Receivers;Zinc;Degraded wiretap channels;Information spectrum method;Information-theoretic security;Strong converse;degraded wiretap channels;information spectrum method;information-theoretic security},
owner = {mattbloch},
timestamp = {2015.01.06}
}


11. R. A. Chou and M. R. Bloch, “Separation of Reliability and Secrecy in Rate-Limited Secret Key-Distillation,” IEEE Transactions on Information Theory, vol. 60, no. 8, pp. 4941–4957, Aug. 2014.

For a discrete or a continuous source model, we study the problem of secret-key generation with one round of rate-limited public communication between two legitimate users. Although we do not provide new bounds on the wiretap secret-key (WSK) capacity for the discrete source model, we use an alternative achievability scheme that may be useful for practical applications. As a side result, we conveniently extend known bounds to the case of a continuous source model. Specifically, we consider a sequential key-generation strategy, that implements a rate-limited reconciliation step to handle reliability, followed by a privacy amplification step performed with extractors to handle secrecy. We prove that such a sequential strategy achieves the best known bounds for the rate-limited WSK capacity (under the assumption of degraded sources in the case of two-way communication). However, we show that, unlike the case of rate-unlimited public communication, achieving the reconciliation capacity in a sequential strategy does not necessarily lead to achieving the best known bounds for the WSK capacity. Consequently, reliability and secrecy can be treated successively but not independently, thereby exhibiting a limitation of sequential strategies for rate-limited public communication. Nevertheless, we provide scenarios for which reliability and secrecy can be treated successively and independently, such as the two-way rate-limited SK capacity, the one-way rate-limited WSK capacity for degraded binary symmetric sources, and the one-way rate-limited WSK capacity for Gaussian degraded sources.

@article{Chou2012a,
author = {Chou, Remi A. and Bloch, Matthieu R},
title = {Separation of Reliability and Secrecy in Rate-Limited Secret Key-Distillation},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2014},
volume = {60},
number = {8},
pages = {4941--4957},
month = aug,
citeseerurl = {1210.4482},
doi = {10.1109/TIT.2014.2323246},
eprint = {1210.4482},
groups = {Secret key agreement},
owner = {mattbloch},
timestamp = {2012.09.24}
}


12. N. Li et al., “Two approaches for ultrafast random bit generation based on the chaotic dynamics of a semiconductor laser,” Optics Express, vol. 22, no. 6, pp. 6634–6646, Mar. 2014.

This paper reports the experimental investigation of two different approaches to random bit generation based on the chaotic dynamics of a semiconductor laser with optical feedback. By computing high-order finite differences of the chaotic laser intensity time series, we obtain time series with symmetric statistical distributions that are more conducive to ultrafast random bit generation. The first approach is guided by information-theoretic considerations and could potentially reach random bit generation rates as high as 160 Gb/s by extracting 4 bits per sample. The second approach is based on pragmatic considerations and could lead to rates of 2.2 Tb/s by extracting 55 bits per sample. The randomness of the bit sequences obtained from the two approaches is tested against three standard randomness tests (ENT, Diehard, and NIST tests), as well as by calculating the statistical bias and the serial correlation coefficients on longer sequences of random bits than those used in the standard tests.

@article{Li2013,
author = {Li, Nianqiang and Kim, Byungchil and Chizhevsky, V. N. and Locquet, A. and Bloch, M. and Citrin, D. S. and Pan, Wei},
title = {Two approaches for ultrafast random bit generation based on the chaotic dynamics of a semiconductor laser},
journal = {{O}ptics {E}xpress},
year = {2014},
volume = {22},
number = {6},
pages = {6634--6646},
month = mar,
doi = {10.1364/OE.22.006634},
groups = {Physical random number generation},
keywords = {Fiber optics and optical communications; Chaos; Semiconductor lasers; Instabilities and chaos},
publisher = {OSA}
}


13. M. R. Bloch and J. N. Laneman, “Strong Secrecy from Channel Resolvability,” IEEE Transactions on Information Theory, vol. 59, no. 12, pp. 8077–8098, Dec. 2013.

We analyze physical-layer security based on the premise that the coding mechanism for secrecy over noisy channels is tied to the notion of channel resolvability. Instead of considering capacity-based constructions, which associate to each message a subcode that operates just below the capacity of the eavesdropper’s channel, we consider channel-resolvability-based constructions, which associate to each message a subcode that operates just above the resolvability of the eavesdropper’s channel. Building upon the work of Csiszár and Hayashi, we provide further evidence that channel resolvability is a powerful and versatile coding mechanism for secrecy by developing results that hold for strong secrecy metrics and arbitrary channels. Specifically, we show that at least for symmetric wiretap channels, random capacity-based constructions fail to achieve the strong secrecy capacity, while channel-resolvability-based constructions achieve it. We then leverage channel resolvability to establish the secrecy-capacity region of arbitrary broadcast channels with confidential messages and a cost constraint for strong secrecy metrics. Finally, we specialize our results to study the secrecy capacity of wireless channels with perfect channel state information (CSI), mixed channels, and compound channels with receiver CSI, as well as the secret-key capacity of source models for secret-key agreement. By tying secrecy to channel resolvability, we obtain achievable rates for strong secrecy metrics with simple proofs.

@article{Bloch2011e,
author = {Bloch, Matthieu R. and Laneman, J. Nicholas},
title = {Strong Secrecy from Channel Resolvability},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2013},
volume = {59},
number = {12},
pages = {8077-8098},
month = dec,
issn = {0018-9448},
citeseerurl = {1105.5419},
doi = {10.1109/TIT.2013.2283722},
eprint = {1105.5419},
file = {:Users/mattbloch/Documents/Publications/2013-Bloch-IEEETransIT.pdf:PDF},
groups = {Wiretap channels},
keywords = {Channel capacity;Encoding;Entropy;Measurement;Mutual information;Random variables;Security;Channel resolvability;information-spectrum;information-theoretic security;secret-key agreement;wireless channels;wiretap channel},
owner = {matthieu},
timestamp = {2009.07.12}
}


14. W. K. Harrison, J. Almeida, M. R. Bloch, S. W. McLaughlin, and J. Barros, “Coding for Secrecy: An Overview of Error-Control Coding Techniques for Physical-Layer Security,” IEEE Signal Processing Magazine, vol. 30, no. 5, pp. 41–50, Sep. 2013.

While secrecy in communication systems has historically been obtained through cryptographic means in the upper layers, recent research efforts have focused on the physical layer and have unveiled ample opportunities for security design. In particular, the combination of signal processing techniques with channel coding for secrecy has been central to the development of physical-layer security efforts. Although implicit coding techniques for secrecy have been known since the 1970s, explicit code constructions have only been discovered within the last decade. The purpose of this article is to provide a synopsis of the state of the art in coding for secrecy. We discuss the general principles of coding, and we illustrate them with several examples. In particular, we discuss the importance of a nested code structure and stochastic encoding, which allow for both data reliability and security.

@article{Harrison2013,
author = {Harrison, Willie K. and Almeida, Joao and Bloch, Matthieu R. and McLaughlin, Steven W. and Barros, Joao},
title = {Coding for Secrecy: An Overview of Error-Control Coding Techniques for Physical-Layer Security},
journal = {{IEEE} {S}ignal {P}rocessing {M}agazine},
year = {2013},
volume = {30},
number = {5},
pages = {41--50},
month = sep,
doi = {10.1109/MSP.2013.2265141},
file = {:Users/mattbloch/Documents/Publications/2013-Harrison-IEEESPMag.pdf:PDF},
groups = {Wiretap codes},
howpublished = {accepted to \emph{Signal Processing Magazine}},
owner = {mattbloch},
quality = {1},
timestamp = {2013.01.20}
}


15. R. Bassily et al., “Cooperative Security at the Physical Layer: A Summary of Recent Advances,” IEEE Signal Processing Magazine, vol. 30, no. 5, pp. 16–28, Sep. 2013.

Wireless communications systems are particularly vulnerable to security attacks because of the inherent openness of the transmission medium. In this article, we focus on guaranteeing confidentiality against eavesdropping attacks where an unauthorized entity aims to intercept an ongoing wireless communication, and we provide a comprehensive summary of recent advances in the area of physical-layer security that guarantees confidentiality by using cooperative techniques unique to the wireless medium. These cooperative techniques consist of carefully designed coding and signaling schemes that are able to harness the properties of the physical layer and to ensure some level of information-theoretic security.

@article{Bassily2013,
author = {Bassily, Raef and Ekrem, Ersen and He, Xiang and Tekin, Ender and Xie, Jianwei and Bloch, Matthieu and Ulukus, Sennur and Yener, Aylin},
title = {Cooperative Security at the Physical Layer: A Summary of Recent Advances},
journal = {{IEEE} {S}ignal {P}rocessing {M}agazine},
year = {2013},
volume = {30},
number = {5},
pages = {16--28},
month = sep,
doi = {10.1109/MSP.2013.2260875},
file = {:2013-Bassily-IEEESPMag.pdf:PDF},
groups = {Cooperative jamming},
howpublished = {accepted to \emph{Signal Processing Magazine}},
owner = {mattbloch},
quality = {1},
timestamp = {2013.01.20}
}


16. M. R. Bloch and J. N. Laneman, “Exploiting Partial Channel State Information for Secrecy over Wireless Channels,” IEEE Journal on Selected Areas in Communications, vol. 31, no. 9, pp. 1840–1849, Sep. 2013.

In this paper, we investigate the effect of partial channel state information on the achievable secure communication rates and secret-key generation rates over ergodic fading channels. In particular, we establish the strong secret-key capacity as well as lower bounds for the strong secrecy capacity of ergodic and block-ergodic fading channels with partial Channel State Information at the Transmitter(CSIT). Our analysis sheds light on the usefulness of CSIT to harness the benefits of fading for secrecy and allows us to quantify the penalty incurred by the lack of full CSIT. In particular, we numerically illustrate situations in which little CSIT is required to recover most of the benefits of fading and in which the legitimate terminals have an incentive to precisely characterize their channel.

@article{Bloch2012b,
author = {Bloch, Matthieu R. and Laneman, J. Nicholas},
title = {Exploiting Partial Channel State Information for Secrecy over Wireless Channels},
journal = {{IEEE} {J}ournal on {S}elected {A}reas in {C}ommunications},
year = {2013},
volume = {31},
number = {9},
pages = {1840-1849},
month = sep,
issn = {0733-8716},
doi = {10.1109/JSAC.2013.130916},
file = {:Users/mattbloch/Documents/Publications/2013-Bloch-IEEEJSAC.pdf:PDF},
groups = {Secret key agreement},
keywords = {Channel state information;Coherence;Communication system security;Encoding;Fading;Resource management;Wireless communication;channels state information;secrecy capacity;secret-key capacity;wireless fading channel}
}


17. F. Renna, M. R. Bloch, and N. Laurenti, “Semi-blind Key-Agreement over MIMO Fading Channels,” IEEE Transactions on Communications, vol. 61, no. 2, pp. 620–627, Feb. 2013.

In this paper, we study the fundamental limits of secret-key agreement over MIMO quasi-static fading channels. We provide closed-form expressions for the secret-key capacity in both the asymptotic high-power and low-power regimes. The optimal signaling strategy for the low-power regime is shown to be independent of the eavesdropper’s channel and secret-key capacity is achieved by transmitting random Gaussian symbols along the direction corresponding to the maximal eigenvalue of the legitimate channel matrix. Hence, by beamforming and waterfilling over the main channel alone, one obtains a semi-blind key-agreement strategy in which the knowledge of the eavesdropper’s channel is only required for privacy amplification. We also derive the probability that a target secret-key rate is not achieved by the optimal low-power signaling when assuming only statistical CSI about the eavesdropper’s channel.

@article{Renna2012,
author = {Renna, Francesco and Bloch, Matthieu R. and Laurenti, Nicola},
title = {{S}emi-blind Key-Agreement over {MIMO} Fading Channels},
journal = {{IEEE} {T}ransactions on {C}ommunications},
year = {2013},
volume = {61},
number = {2},
pages = {620--627},
month = feb,
doi = {10.1109/TCOMM.2012.102512.120084},
file = {:../Publications/2013-Renna-IEEETransCom.pdf:PDF},
groups = {Secret key agreement},
howpublished = {accepted to \emph{IEEE Transactions on Communications}},
owner = {mattbloch},
timestamp = {2012.01.29}
}


18. A. Subramanian, A. Thangaraj, M. Bloch, and S. McLaughlin, “Strong Secrecy on the Binary Erasure Wiretap Channel Using Large-Girth LDPC Codes,” IEEE Transactions on Information Forensics and Security, vol. 6, no. 3, pp. 585–594, Sep. 2011.

For an arbitrary degree distribution pair (DDP), we construct a sequence of low-density parity-check (LDPC) code ensembles with girth growing logarithmically in block-length using Ramanujan graphs. When the DDP has minimum left degree at least three, we show using density evolution analysis that the expected bit-error probability of these ensembles, when passed through a binary erasure channel with erasure probability ε, decays as O (exp(-( c 1 ) n(c 2 ))) with the block-length n for positive constants c 1 and c 2 , as long as εis less than the erasure threshold εth of the DDP. This guarantees that the coset coding scheme using the dual sequence provides strong secrecy over the binary erasure wiretap channel for erasure probabilities greater than 1-\epsilonth .

@article{Subramanian2011,
author = {Subramanian, Arunkumar and Thangaraj, Andrew and Bloch, Matthieu and McLaughlin, Steven},
title = {{S}trong Secrecy on the Binary Erasure Wiretap Channel Using Large-Girth {LDPC} Codes},
journal = {{IEEE} {T}ransactions on {I}nformation {F}orensics and {S}ecurity},
year = {2011},
volume = {6},
number = {3},
pages = {585--594},
month = sep,
citeseerurl = {1009.3130},
doi = {10.1109/TIFS.2011.2148715},
file = {:2011-Subramanian-IEEETransIFS.pdf:PDF},
groups = {Wiretap codes},
howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}},
owner = {matthieu},
timestamp = {2010.09.19}
}


19. A. J. Pierrot and M. R. Bloch, “Strongly Secure Communications Over the Two-Way Wiretap Channel,” IEEE Transactions on Information Forensics and Security, vol. 6, no. 3, pp. 595–605, Sep. 2011.

We consider the problem of secure communications over the two-way wiretap channel under a strong secrecy criterion. We improve existing results by developing an achievable region based on strategies that exploit both the interference at the eavesdropper’s terminal and cooperation between legitimate users. We leverage the notion of channel resolvability for the multiple-access channel to analyze cooperative jamming and we show that the artificial noise created by cooperative jamming induces a source of common randomness that can be used for secret-key agreement. We illustrate the gain provided by this coding technique in the case of the Gaussian two-way wiretap channel, and we show significant improvements for some channel configurations.

@article{Pierrot2011a,
author = {Pierrot, Alexandre J. and Bloch, Matthieu R.},
title = {{S}trongly Secure Communications Over the Two-Way Wiretap Channel},
journal = {{IEEE} {T}ransactions on {I}nformation {F}orensics and {S}ecurity},
year = {2011},
volume = {6},
number = {3},
pages = {595--605},
month = sep,
citeseerurl = {1010.0177},
doi = {10.1109/TIFS.2011.2158422},
file = {:2011-Pierrot-IEEETransIFS.pdf:PDF},
groups = {Wiretap channels},
howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}},
owner = {matthieu},
timestamp = {2010.08.29}
}


20. J. P. Vilela, M. Bloch, J. Barros, and S. W. McLaughlin, “Wireless Secrecy Regions with Friendly Jamming,” IEEE Transactions on Information Forensics and Security, vol. 6, no. 2, pp. 256–266, Jun. 2011.

Inspired by recent results on information-theoretic security, we consider the transmission of confidential messages over wireless networks, in which the legitimate communication partners are aided by friendly jammers. We characterize the security level of a confined region in a quasi-static fading environment by computing the probability of secrecy outage in connection with two new measures of physical-layer security: the jamming coverage and the jamming efficiency. Our analysis for various jamming strategies based on different levels of channel state information provides insight into the design of optimal jamming configurations and shows that a single jammer is not sufficient to maximize both figures of merit simultaneously. Moreover, a single jammer requires full channel state information to provide security gains in the vicinity of the legitimate receiver.

@article{Vilela2011,
author = {Vilela, Joao Paulo and Bloch, Matthieu and Barros, Joao and McLaughlin, Steven W.},
title = {{W}ireless Secrecy Regions with Friendly Jamming},
journal = {{IEEE} {T}ransactions on {I}nformation {F}orensics and {S}ecurity},
year = {2011},
volume = {6},
number = {2},
pages = {256--266},
month = jun,
doi = {10.1109/TIFS.2011.2111370},
file = {:2011-Vilela-IEEETransIFS.pdf:PDF;:Vilela2011 - {W}ireless Secrecy Regions with Friendly Jamming.pdf:PDF},
groups = {Wiretap channels},
howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}},
owner = {matthieu},
timestamp = {2009.11.17}
}


21. T. F. Wong, M. Bloch, and J. M. Shea, “Secret Sharing over Fast-Fading MIMO Wiretap Channels,” EURASIP Journal on Wireless Communications and Networking, vol. 2009, pp. 506973/1–17, 2009.

Secret sharing over the fast-fading MIMO wiretap channel is considered. A source and a destination try to share secret information over a fast-fading MIMO channel in the presence of an eavesdropper who also makes channel observations that are different from but correlated to those made by the destination. An interactive, authenticated public channel with unlimited capacity is available to the source and destination for the secret sharing process. This situation is a special case of the "channel model with wiretapper" considered by Ahlswede and Csiszár. An extension of their result to continuous channel alphabets is employed to evaluate the key capacity of the fast-fading MIMO wiretap channel. The effects of spatial dimensionality provided by the use of multiple antennas at the source, destination, and eavesdropper are then investigated.

@article{Wong2009,
author = {Wong, Tan F. and Bloch, Matthieu and Shea, John M.},
title = {{S}ecret Sharing over Fast-Fading {MIMO} Wiretap Channels},
journal = {{EURASIP} {J}ournal on {W}ireless {C}ommunications and {N}etworking},
year = {2009},
volume = {2009},
pages = {506973/1-17},
citeseerurl = {cs.IT/0812.2719},
doi = {10.1155/2009/506973},
file = {:2009-Wong-EURASIP.pdf:PDF},
groups = {Secret key agreement, Wireless security},
howpublished = {accepted to EURASIP Journal on Wireless Communications and Networking},
owner = {matthieu},
timestamp = {2009.09.10}
}


22. M. Bloch, R. Narasimha, and S. W. McLaughlin, “Network Security for Client-Server Architecture using Wiretap Codes,” IEEE Transactions on Information Forensics and Security, vol. 3, no. 3, pp. 404–413, Sep. 2008.

We propose a method that provides information-theoretic security for client-server communications. By introducing an appropriate encoding scheme, we show how a client-server architecture under active attacks can be modeled as a binary-erasure wiretap channel. The secrecy capacity of the equivalent wiretap channel is then used as a metric to optimize the architecture and limit the impact of the attacks. Upper and lower bounds of the optimal secrecy capacity are derived and analyzed. While still mostly of theoretical interest, our analysis sheds some light on the practical design of resistant and secure client-server architectures.

@article{Bloch2008d,
author = {Bloch, Matthieu and Narasimha, Rajesh and McLaughlin, Steven W.},
title = {{N}etwork Security for Client-Server Architecture using Wiretap Codes},
journal = {{IEEE} {T}ransactions on {I}nformation {F}orensics and {S}ecurity},
year = {2008},
volume = {3},
number = {3},
pages = {404--413},
month = sep,
doi = {10.1109/TIFS.2008.927688},
file = {:2008-Bloch-IEEETransIFS.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2007.10.01}
}


23. M. Bloch, J. Barros, M. R. D. Rodrigues, and S. W. McLaughlin, “Wireless Information-Theoretic Security,” IEEE Transactions on Information Theory, vol. 54, no. 6, pp. 2515–2534, Jun. 2008.

This paper considers the transmission of confidential data over wireless channels. Based on an information-theoretic formulation of the problem, in which two legitimates partners communicate over a quasi-static fading channel and an eavesdropper observes their transmissions through a second independent quasi-static fading channel, the important role of fading is characterized in terms of average secure communication rates and outage probability. Based on the insights from this analysis, a practical secure communication protocol is developed, which uses a four-step procedure to ensure wireless information-theoretic security: (i) common randomness via opportunistic transmission, (ii) message reconciliation, (iii) common key generation via privacy amplification, and (iv) message protection with a secret key. A reconciliation procedure based on multilevel coding and optimized low-density parity-check (LDPC) codes is introduced, which allows to achieve communication rates close to the fundamental security limits in several relevant instances. Finally, a set of metrics for assessing average secure key generation rates is established, and it is shown that the protocol is effective in secure key renewal-even in the presence of imperfect channel state information.

@article{Bloch2008c,
author = {Bloch, Matthieu and Barros, Jo{\~a}o and Rodrigues, Miguel R. D. and McLaughlin, Steven W.},
title = {{W}ireless Information-Theoretic Security},
journal = {{IEEE} {T}ransactions on {I}nformation {T}heory},
year = {2008},
volume = {54},
number = {6},
pages = {2515--2534},
month = jun,
citeseerurl = {cs.IT/0611120,cs.IT/0611121},
comment = {Preprint cited 3 times 1. The Wiretap Channel with Feedback: Encryption over the Channel, Lai, L.; Gamal, H. E. & Poor, H. V., 2007 Allerton Conference on Communication, Control and Computing. 2. The Secrecy Capacity of the MIMO wiretap channel, Oggier, F. & Hassibi, B., 2007 Allerton Conference on Communication, Control and Computing. 3. Dense Parity Check Based Secrecy Sharing in Wireless Communications, Xiao S; Pishro-Nik,H & Gong, W., 2007 Globecom conference.},
doi = {10.1109/TIT.2008.921908},
file = {:2008-Bloch-IEEETransIT.pdf:PDF},
groups = {Wireless security},
owner = {matthieu},
timestamp = {2007.10.01}
}


24. J. Lodewyck et al., “Quantum key distribution over 25 km with an all-fiber continuous-variable system,” Physical Review A, vol. 76, pp. 042305/1–10, Oct. 2007.

We report on the implementation of a reverse-reconciliated coherent-state continuous-variable quantum key distribution system, with which we generated secret keys at a rate of more than 2 kb/s over 25 km of optical fiber. Time multiplexing is used to transmit both the signal and phase reference in the same optical fiber. Our system includes all experimental aspects required for a field implementation of a quantum key distribution setup. Real-time reverse reconciliation is achieved by using fast and efficient LDPC error correcting codes.

@article{Lodewyck2007,
author = {Lodewyck, J\'erome and Bloch, Matthieu and Garc\'ia-Patr\'on, Ra\'ul and Fossier, Simon and Karpov, Evgueni and Diamanti, Eleni and Debuisschert, Thierry and Cerf, Nicolas J. and Tualle-Brouri, Rosa and McLaughlin, Steven W. and Grangier, Philippe},
title = {{Q}uantum key distribution over 25 km with an all-fiber continuous-variable system},
journal = {{P}hysical {R}eview {A}},
year = {2007},
volume = {76},
pages = {042305/1-10},
month = oct,
citeseerurl = {0706.4255},
comment = {Cited 2 times 1. Experimental study on the Gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers, Bing Qi, Lei-Lei Huang, Li Qian, and Hoi-Kwong Lo, Phys. Rev. A, 76, 052323, 2007 2. Two-way quantum key distribution at telecommunication wavelength, Rupesh Kumar, Marco Lucamarini, Giovanni Di Giuseppe, Riccardo Natali, Giorgio Mancini, and Paolo Tombesi, Phys. Rev. A, 77, 022304, 2008},
doi = {10.1103/PhysRevA.76.042305},
file = {:Users/matthieu/Documents/publications/2007-Lodewyck-PhysRevA.pdf:PDF},
groups = {Quantum key distribution},
owner = {matthieu},
timestamp = {2007.10.01}
}


25. M. Bloch, S. W. McLaughlin, F. Patois, and J.-M. Merolla, “Frequency-Coded Quantum Key Distribution,” Optics Letters, vol. 32, no. 3, pp. 301–303, Feb. 2007.

We report an intrinsically stable quantum key distribution scheme based on genuine frequency-coded quantum states. The qubits are efficiently processed without fiber interferometers by fully exploiting the nonlinear interaction occurring in electro-optic phase modulators. The system requires only integrated off-the-shelf devices and could be used with a true single-photon source. Preliminary experiments have been performed with weak laser pulses and have demonstrated the feasibility of this new setup.

@article{Bloch2007,
author = {Bloch, Matthieu and McLaughlin, Steven W. and Patois, Fr\'ed\'eric and Merolla, Jean-Marc},
title = {{F}requency-Coded Quantum Key Distribution},
journal = {{O}ptics {L}etters},
year = {2007},
volume = {32},
number = {3},
pages = {301--303},
month = feb,
doi = {doi:10.1364/OL.32.000301},
file = {:Users/matthieu/Documents/publications/2007-Bloch-OptLett.pdf:PDF;2007-Bloch-OptLett.pdf:2007-Bloch-OptLett.pdf:PDF},
groups = {Quantum key distribution, Experiments},
keywords = {Fiber optics and optical communications Quantum optics},
owner = {Matthieu},
timestamp = {2006.11.15}
}


26. S. Donnet, A. Thangaraj, M. Bloch, J. Cussey, J.-M. Merolla, and L. Larger, “Security of Y-00 under heterodyne measurement and fast correlation attack,” Physics Letters A, vol. 356, no. 6, pp. 406–410, Aug. 2006.

We provide a security analysis of the Y-00 protocol under heterodyne measurement and correlation attack. We show that the secrecy of the data encryption scheme is extremely sensitive to the running-key generation process. In many situations our simple attack succeeds in recovering the initial shared secret key. Our simulation results suggest that a truly secure implementation of the protocol should take into account the effective key generation method.

@article{Donnet2006,
author = {Donnet, St\'ephane and Thangaraj, Andrew and Bloch, Matthieu and Cussey, Johann and Merolla, Jean-Marc and Larger, Laurent},
title = {{S}ecurity of {Y}-00 under heterodyne measurement and fast correlation attack},
journal = {{P}hysics {L}etters {A}},
year = {2006},
volume = {356},
number = {6},
pages = {406--410},
month = aug,
comment = {Cited 4 times 1. Ahn C, Birnbaum K Exposed-key weakness of alpha eta PHYSICS LETTERS A 370(2) 2007 2. Hirota O Practical security analysis of a quantum stream cipher by the Yuen 2000 protocol PHYSICAL REVIEW A 3 76(3) 2007 3. Mihaljevic MJ Generic framework for the secure Yuen 2000 quantum-encryption protocol employing the wire-tap channel approach PHYSICAL REVIEW A 75(5) 2007 4. Yuen HP, Nair R On the security of Y-00 under fast correlation and other attacks on the key PHYSICS LETTERS A, 364(2), 2007},
doi = {10.1016/j.physleta.2006.04.002},
file = {:Users/matthieu/Documents/publications/2006-Donnet-PhysLettA.pdf:PDF;2006-Donnet-PhysLettA.pdf:2006-Donnet-PhysLettA.pdf:PDF},
groups = {Quantum key distribution},
owner = {Matthieu},
timestamp = {2006.11.15}
}


### Conference proceedings

1. I. A. Kadampot, M. Tahmasbi, and M. R. Bloch, “Multilevel-Coded Pulse Position Modulation for Covert Communications,” in Proc. of IEEE International Symposium on Information Theory, Vail, CO, Jun. 2018, pp. 1864–1868.

We develop a low-complexity coding scheme to achieve covert communications over binary symmetric channels. We circumvent the impossibility of covert communication with linear codes by introducing non-linearity through the use of pulse-position modulation (PPM) and multilevel coding (MLC). We show that the MLC-PPM scheme exhibits many appealing properties, in particular, the channel at a given index level remains the same as the number of level increases, which allows one to use families of capacity- and resolvability-achieving codes to concretely instantiate the covert communication scheme.

@inproceedings{Kadampot2018,
author = {Kadampot, Ishaque Ashar and Tahmasbi, Mehrdad and Bloch, Matthieu R.},
title = {Multilevel-Coded Pulse Position Modulation for Covert Communications},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2018},
pages = {1864--1868},
month = jun,
doi = {10.1109/ISIT.2018.8437587},
groups = {Steganography and covert communications},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


2. K. Arumugam, M. R. Bloch, and L. Wang, “Covert Communication over a Physically Degraded Relay Channel with Non-Colluding Wardens,” in Proc. of IEEE International Symposium on Information Theory, Vail, CO, Jun. 2018, pp. 766–770.

We analyze a physically degraded relay channel, in which the transmitter sends a covert message to the legitimate receiver with the help of a relay. Two wardens, who do not collude with each other, monitor communication from the transmitter and the relay, respectively, through two Discrete Memoryless Channels (DMCs) to detect the presence of a covert message. The objective of the transmitter is to deliver the covert message successfully to the receiver without exceeding the covertness threshold of either warden. We identify the optimal asymptotic scaling of message and key bits and the dependence of the covert throughput on the two covertness thresholds.

@inproceedings{Arumugam2018,
author = {Arumugam, Keerthi and Bloch, Matthieu R and Wang, Ligong},
title = {Covert Communication over a Physically Degraded Relay Channel with Non-Colluding Wardens},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2018},
pages = {766--770},
month = jun,
doi = {10.1109/ISIT.2018.8437505},
groups = {Steganography and covert communications},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


3. N. Helhal, M. R. Bloch, and A. Nosratinia, “Multiple-Access Channel Resolvability with Cribbing,” in Proc. IEEE International Symposium on Information Theory, Vail, CO, Jun. 2018, pp. 2052–2056.

We study channel resolvability for the discrete memoryless multiple access channel with cribbing, i.e., the characterization of the amount of randomness required to approximate an i.i.d. output distribution in terms of Kullback-Leibler divergence. We analyze the cases in which one encoder cribs (i) the input of the other encoder; or the output of the other encoder (ii) noncausally, (iii) causally, or (iv) strictly-causally. For cases (i)-(iii), we exactly characterize the channel resolvability region. For case (iv), we provide inner and outer bounds for the channel resolvability region; our achievability result handles the strict causality constraint with a block-Markov coding scheme in which dependencies across blocks are suitably hidden.

@inproceedings{Helhal2018,
author = {Helhal, Noha and Bloch, Matthieu R and Nosratinia, Aria},
title = {Multiple-Access Channel Resolvability with Cribbing},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2018},
pages = {2052--2056},
month = jun,
doi = {10.1109/ISIT.2018.8437580},
file = {:2018-Helal-ISIT.pdf:PDF},
groups = {Randomness processing},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
issn = {2157-8117},
keywords = {channel capacity;channel coding;Markov processes;memoryless systems;multi-access systems;discrete memoryless multiple access channel;cribbing;output distribution;Kullback-Leibler divergence;encoder cribs;channel resolvability region;strict causality constraint;multiple-access channel resolvability;block-Markov coding scheme;Encoding;Zirconium;Recycling;Random variables;Delays;Zinc}
}


4. K. S. K. Arumugam and M. R. Bloch, “Covert communication over broadcast channels,” in Proc. of IEEE Information Theory Workshop, Kaohsiung, Taiwan, Nov. 2017, pp. 299–303.

We analyze a two-receiver binary-input discrete memoryless broadcast channel, in which the transmitter communicates a common message simultaneously to both users and a covert message to only one of them while treating the other as an adversary. This model captures the problem of embedding covert messages in an innocuous codebook and generalizes previous models in which the innocent behavior corresponds to the absence of communication between legitimate users. We identify the exact asymptotic behavior of the number of reliable and covert bits when the rate of the innocuous codebook is close to the channel capacity of the adversary. In particular, our results characterize the dependence of the number of covert bits on the channel parameters and the characteristics of the innocent codebook.

@inproceedings{Arumugam2017,
author = {Arumugam, K. S. K. and Bloch, M. R.},
title = {Covert communication over broadcast channels},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2017},
pages = {299--303},
month = nov,
doi = {10.1109/ITW.2017.8278022},
file = {:2017-Arumugam-ITW.pdf:PDF},
groups = {Steganography and covert communications}
}


5. M. Tahmasbi, M. R. Bloch, and V. F. Tan, “Error exponents covert communications,” in Proc. of IEEE Information Theory Workshop, Kaohsiung, Taiwan, Nov. 2017, pp. 304–308.

We define and study the error exponent of covert communications over binary-input Discrete Memoryless Channels (DMCs). Our main result consists of upper and lower bounds for the exponent, which match in a regime that we explicitly characterize. While our proofs follow standard techniques, the vanishing rate regime inherent to covert communications and the low-weight of codewords introduces specific technical challenges. In particular, the lower bound of the error exponent follows from a non-standard constant-composition ensemble instead of an independent and identically distributed (i.i.d.) ensemble, and the upper bound requires a careful treatment that does not appear in the traditional analysis of error exponent.

@inproceedings{Tahmasbi2017b,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R and Tan, Vincent F},
title = {Error exponents covert communications},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2017},
pages = {304-308},
month = nov,
doi = {10.1109/ITW.2017.8278024},
groups = {Steganography and covert communications}
}


6. M. Tahmasbi and M. R. Bloch, “Covert secret key generation,” in Proc. of IEEE Conference on Communications and Network Security, Workshop on Physical-Layer Methods for Wireless Security, Las Vegas, NV, Oct. 2017, pp. 540–544.

We investigate the possibility of covert and secret key generation over a discrete memoryless channel model with one way public discussion. Protocols are required to conceal not only the key but also whether a protocol is being implemented. For some models, we show that covert secret key generation is possible and characterize the covert secret key capacity in special cases; in particular, the covert secret key capacity is sometimes equal to the covert capacity of the channel, so that secrecy comes ï¿½for free.ï¿½ Our main contribution is the analysis of a protocol that exploits the likelihood encoder to circumvent source coding with side information and privacy amplification.

@inproceedings{Tahmasbi2017c,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R.},
title = {Covert secret key generation},
booktitle = {Proc. of IEEE Conference on Communications and Network Security, Workshop on Physical-Layer Methods for Wireless Security},
year = {2017},
pages = {540-544},
month = oct,
doi = {10.1109/CNS.2017.8228681},
groups = {Steganography and covert communications, Secret key agreement},
keywords = {Communication networks;Communication system security;Conferences;Privacy;Protocols;Security;Throughput}
}


7. H. Zivari-Fard, M. Bloch, and A. Nosratinia, “Two-Transmitter Two-Receiver Channel with Confidential Messages,” in Proc. of Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2017.

We study the two-transmitter two-receiver channel with confidential messages channel under a secrecy constraint, exploring the effect of a single eavesdropper on the secure communication rate. A general achievable secrecy rate region and an outer bound are derived for the degraded version of this channel. An example is provided in which the inner and outer bound meet. For the general non-degraded channel, another outer bound is derived and a special case is highlighted in which the inner and outer bound meet. Our inner bound recovers the known inner bounds for the multiple-access wiretap channel, broadcast channel with confidential messages, and the compound MAC channel.

@inproceedings{Zivari-Fard2017,
author = {Zivari-Fard, Hassan and Bloch, Matthieu and Nosratinia, Aria},
title = {Two-Transmitter Two-Receiver Channel with Confidential Messages},
booktitle = {Proc. of Allerton Conference on Communication, Control, and Computing},
year = {2017},
month = sep,
doi = {10.1109/ALLERTON.2017.8262725},
groups = {Wiretap channels},
howpublished = {accepted to \emph{Allerton Conference on Communication Control and Computing}}
}


8. E. Shipilova, J.-L. Boelle, M. Barret, M. Bloch, and J.-L. Collette, “Separation of impulsive blended seismic sources using Orthogonal Matching Pursuit,” in 79th Annual International Conference and Exhibition EAGE, Paris, France, Jun. 2017.

@inproceedings{Shipilova2017a,
author = {Shipilova, Ekaterina and Boelle, Jean-Luc and Barret, Michel and Bloch, Matthieu and Collette, Jean-Luc},
title = {Separation of impulsive blended seismic sources using Orthogonal Matching Pursuit},
booktitle = {79th Annual International Conference and Exhibition EAGE},
year = {2017},
month = jun,
doi = {10.3997/2214-4609.201700875}
}


9. M. Tahmasbi, M. R. Bloch, and A. Yener, “Learning Adversary’s Actions for Secret Communication,” in Proc. of IEEE International Symposium on Information Theory, Aachen, Germany, Jun. 2017, pp. 2713–2717.

We analyze the problem of secure communication over a wiretap channel with an active adversary, in which the legitimate transmitter has the opportunity to sense and learn the adversary’s actions. Specifically, the adversary has the ability to switch between two channels and to observe the corresponding output at every channel use; the encoder, however, has causal access to observations impacted by adversary’s actions. We develop a joint learning/transmission scheme in which the legitimate users learn and adapt to the adversary’s actions. For some channel models, we show that the achievable rates, which we define precisely, are arbitrarily close to those obtained with hindsight, had the transmitter known the actions ahead of time. This suggests that there is much to exploit and gain in physical-layer security by monitoring the environment.

@inproceedings{Tahmasbi2017a,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R and Yener, Aylin},
title = {Learning Adversary's Actions for Secret Communication},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2017},
pages = {2713--2717},
month = jun,
doi = {10.1109/ISIT.2017.8007021},
file = {:2017-Tahmasbi-ISIT.pdf:PDF},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


10. I. A. Kadampot and M. R. Bloch, “Coordination with Clustered Common Randomness in a Three-Terminal Line Network,” in Proc. of IEEE International Symposium on Information Theory, Aachen, Germany, Jun. 2017, pp. 1828–1832.

To achieve strong coordination in a network, nodes benefit from access to a source of common randomness. Most studies pertaining to strong coordination assume the existence of a source of common randomness accessible to all nodes in the network. This assumption, however, is not practical in a decentralized network. We analyze the problem of strong coordination in a three-terminal line network with common randomness available only at the first two nodes and assume that the actions of the first node are specified by an external agent. We use coding schemes developed for channel resolvability codes to characterize the strong coordination capacity region when the intermediate node is operating in a functional mode. A comparison of our coordination capacity region with a case in which all nodes have access to a common randomness shows that we have to increase the communication rate between the second and the third nodes to achieve the same coordination distribution.

@inproceedings{Kadampot2017,
author = {Kadampot, Ishaque Ashar and Bloch, Matthieu R},
title = {Coordination with Clustered Common Randomness in a Three-Terminal Line Network},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2017},
pages = {1828--1832},
month = jun,
doi = {10.1109/ISIT.2017.8006845},
groups = {Coordination of networks},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


11. G. Cervia, L. Luzzi, M. L. Treust, and M. R. Bloch, “Strong Coordination of Signals and Actions over Noisy Channels,” in Proc. of IEEE International Symposium on Information Theory, Aachen, Germany, Jun. 2017, pp. 2845–2849.

We develop a random binning scheme for strong coordination in a network of two nodes separated by a noisy channel, in which the input and output signals have to be coordinated with the source and its reconstruction. In the case of non-causal encoding and decoding, we propose a joint source-channel coding scheme and develop inner and outer bounds for the strong coordination region. While the set of achievable target distributions is the same as for empirical coordination, we characterize the rate of common randomness required for strong coordination.

@inproceedings{Cervia2017,
author = {Cervia, Giulia and Luzzi, Laura and Treust, Ma\"el Le and Bloch, Matthieu R},
title = {Strong Coordination of Signals and Actions over Noisy Channels},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2017},
pages = {2845--2849},
month = jun,
doi = {10.1109/ISIT.2017.8007047},
groups = {Coordination of networks},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


12. M. R. Bloch and S. Guha, “Optimal Covert Communications using Pulse-Position Modulation,” in Proc. of IEEE International Symposium on Information Theory, Aachen, Germany, Jun. 2017, pp. 2835–2839.

This paper shows the optimality of Pulse-Position Modulation (PPM) for covert communications over discrete-memoryless channels. Specifically, the concatenation of a random m-ary outer code of length O(m) and an inner code consisting of PPM of order m achieves the information-theoretic limits of covert communications. This suggests alternative code constructions for covert communications, in which the sparsity of the PPM symbols ensures covertness and an appropriate choice of the blocklength results in the square root law.

@inproceedings{Bloch2017,
author = {Bloch, Matthieu R and Guha, Saikat},
title = {Optimal Covert Communications using Pulse-Position Modulation},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2017},
pages = {2835--2839},
month = jun,
doi = {10.1109/ISIT.2017.8007045},
groups = {Steganography and covert communications},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}}
}


13. G. Frèche, M. R. Bloch, and M. Barret, “Polar codes for covert communications over asynchronous Discrete Memoryless Channels,” in Proc. of 51st Annual Conference on Information Sciences and Systems, Baltimore, MD, Mar. 2017, pp. 1–1.

We develop a covert communication scheme for binary-input asynchronous Discrete Memoryless Channels based on binary polar codes, in which legitimate parties exploit uncertainty created by both the channel noise and the time of transmission. The proposed code jointly ensures reliable communication for a legitimate receiver and low probability of detection with respect to an adversary, both observing noisy versions of the codewords. Binary polar codes are used to shape the weight distribution of codewords and ensure that the average weight decays as the block length grows. The performance of the proposed code is limited by the speed of polarization, which in turns controls the decay of the average codeword weight with the block length. Although the proposed construction falls short of achieving the performance of random codes, it inherits the low-complexity properties of polar codes.

@inproceedings{Freche2017a,
author = {Fr\eche, G. and Bloch, M. R. and Barret, M.},
title = {Polar codes for covert communications over asynchronous Discrete Memoryless Channels},
booktitle = {Proc. of 51st Annual Conference on Information Sciences and Systems},
year = {2017},
pages = {1-1},
month = mar,
doi = {10.1109/CISS.2017.7926132},
groups = {Steganography and covert communications, Polar codes},
owner = {mattbloch},
timestamp = {2017.08.30}
}


14. K. S. K. Arumugam, I. A. Kadampot, M. Tahmasbi, S. Shah, M. Bloch, and S. Pokutta, “Modulation recognition using side information and hybrid learning,” in Proc. IEEE Int. Symp. Dynamic Spectrum Access Networks (DySPAN), Piscataway, NJ, Mar. 2017, pp. 1–2.

Recent applications of machine learning to modulation recognition have demonstrated the potential of deep learning to achieve state-of-the-art performance. We propose to further extend this approach by using flexible time-space decompositions that are more in line with the actual learning task, as well as integrate side-information, such as higher order moments, directly into the training process. Our promising preliminary results suggest that there are many more benefits to be reaped from such approaches.

@inproceedings{Arumugam2017a,
author = {Arumugam, K. S. Kumar and Kadampot, I. A. and Tahmasbi, M. and Shah, S. and Bloch, M. and Pokutta, S.},
title = {Modulation recognition using side information and hybrid learning},
booktitle = {Proc. IEEE Int. Symp. Dynamic Spectrum Access Networks (DySPAN)},
year = {2017},
pages = {1--2},
month = mar,
doi = {10.1109/DySPAN.2017.7920750},
groups = {Steganography and covert communications},
keywords = {learning (artificial intelligence), modulation, telecommunication computing, deep learning, flexible time-space decompositions, higher order moments, machine learning, modulation recognition, side information, Cognitive radio, Convolution, Dynamic spectrum access, Machine learning, Modulation, Network architecture, Signal to noise ratio}
}


15. M. Tahmasbi and M. R. Bloch, “Second Order Asymptotics for Degraded Wiretap Channels: How Good Are Existing Codes?,” in 54th Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2016, pp. 830–837.

We develop three new results regarding the second-order asymptotics of secure communication over wiretap channels. We first establish the optimal second-order asymptotics for a class of degraded wiretap channels without feedback under an effective secrecy criterion. We then derive the optimal second-order asymptotics for degraded wiretap channels with feedback. We finally develop a new converse bound for channel resolvability with non-capacity achieving distributions, which we use to develop useful converse bounds for asymmetric degraded wiretap channels. Our results are illustrated with several numerical examples, and suggest that known coding techniques already achieve their best performance.

@inproceedings{Tahmasbi2016a,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R.},
title = {Second Order Asymptotics for Degraded Wiretap Channels: How Good Are Existing Codes?},
booktitle = {54th Annual Allerton Conference on Communication, Control, and Computing},
year = {2016},
pages = {830-837},
month = sep,
doi = {10.1109/ALLERTON.2016.7852319},
groups = {Wiretap channels},
keywords = {encoding;telecommunication security;asymmetric degraded wiretap channels;channel resolvability;converse bound;effective secrecy criterion;existing codes;known coding techniques;optimal second-order asymptotics;secure communication;Decoding;Encoding;Measurement;Monte Carlo methods;Receivers;Reliability;Transmitters}
}


16. K. S. K. Arumugam and M. R. Bloch, “Keyless asynchronous covert communication,” in Proc. of IEEE Information Theory Workshop, Cambridge, United Kingdom, Sep. 2016, pp. 191–195.

We consider a scenario in which Alice asynchronously communicates with Bob over a Discrete Memoryless Channel (DMC) while escaping detection from an adversary who observes their communication through another DMC. Specifically, Alice transmits codewords of length n and chooses the transmission epoch T uniformly at random among N available time epochs, where N >> n. This deliberate symbol level-asynchronism forces the adversary to monitor a window of size N much larger than the codeword length n, and results in an increased covert throughput compared to the scenario without asynchronism. Our result generalizes a previous work in which asynchronism was introduced at the codeword level, i.e., having Alice choose a transmission window among non-overlapping windows of length n.

@inproceedings{Arumugam2016a,
author = {Arumugam, K. S. K. and Bloch, M. R.},
title = {Keyless asynchronous covert communication},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2016},
pages = {191-195},
month = sep,
doi = {10.1109/ITW.2016.7606822},
groups = {Steganography and covert communications},
keywords = {Conferences;Monitoring},
owner = {mattbloch},
timestamp = {2016.03.20}
}


17. G. Cervia, L. Luzzi, M. R. Bloch, and M. L. Treust, “Polar coding for empirical coordination of signals and actions over noisy channels,” in Proc. of IEEE Information Theory Workshop, Cambridge, United Kingdom, Sep. 2016, pp. 81–85.

We develop a polar coding scheme for empirical coordination in a two-node network with a noisy link in which the input and output signals have to be coordinated with the source and the reconstruction. In the case of non-causal encoding and decoding, we show that polar codes achieve the best known inner bound for the empirical coordination region, provided that a vanishing rate of common randomness is available. This scheme provides a constructive alternative to random binning and coding proofs.

@inproceedings{Cervia2016,
author = {Cervia, G. and Luzzi, L. and Bloch, M. R. and Treust, M. Le},
title = {Polar coding for empirical coordination of signals and actions over noisy channels},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2016},
pages = {81-85},
month = sep,
doi = {10.1109/ITW.2016.7606800},
groups = {Coordination of networks},
keywords = {Conferences;Decoding;Electronic mail;Encoding;Noise measurement},
owner = {mattbloch},
timestamp = {2016.03.20}
}


18. R. A. Chou, M. R. Bloch, and A. Yener, “Universal covertness for Discrete Memoryless Sources,” in 54th Annual Allerton Conference on Communication, Control, and Computing (Allerton), Monticello, IL, Aug. 2016, pp. 516–523.

Consider a sequence S of length n emitted by a Discrete Memoryless Source (DMS) with unknown distribution p. We wish to construct a lossless source code that maps S to a sequence S’ of minimal length m such that S’ approximates in terms of Kullback-Leibler divergence a sequence emitted by another DMS with known distribution q. Our main result is the existence of a coding scheme that performs such a task with an asymptotically optimal compression rate, i.e., such that the limit of m/n is H(p)/H(q) as n goes to infinity. Our coding scheme overcomes the challenges created by the lack of knowledge about p by relying on a sufficiently fine estimation of H(p), followed by an appropriately designed type-based compression that jointly performs source resolvability and universal lossless source coding. Our result recovers several previous results that either assume p uniform, or q uniform, or p known. The price paid for these generalizations is the use of common randomness with vanishing rate. We further determine that the length of the latter roughly scales as the square root of n, by an analysis of second order asymptotics and error exponents.

@inproceedings{Chou2016,
author = {Chou, Remi A. and Bloch, Matthieu R. and Yener, Aylin},
title = {Universal covertness for Discrete Memoryless Sources},
booktitle = {54th Annual Allerton Conference on Communication, Control, and Computing (Allerton)},
year = {2016},
pages = {516-523},
month = aug,
doi = {10.1109/ALLERTON.2016.7852275},
groups = {Steganography and covert communications},
keywords = {source coding;DMS;discrete memoryless source;error exponent analysis;second order asymptotic analysis;source resolvability;universal covertness;universal lossless source coding;Decoding;Entropy;Estimation;Random variables;Reliability;Source coding},
owner = {mattbloch},
timestamp = {2016.01.26}
}


19. B. N. Vellambi, J. Kliewer, and M. R. Bloch, “Lossy Compression with Near-uniform Encoder Outputs,” in Proc. of IEEE International Symposium on Information Theory, Barcelona, Spain, Jul. 2016, pp. 530–534.

It is well known that lossless compression of a discrete memoryless source with near-uniform encoder output is possible at a rate above its entropy if and only if the encoder and decoder share a common random seed. This work focuses on deriving conditions for near-uniform encoder output(s) in the Wyner-Ziv and the distributed lossy compression problems. We show that in the Wyner-Ziv problem, near-uniform encoder output and operation close to the WZ-rate limit is simultaneously possible, whereas in the distributed lossy compression problem, jointly near-uniform outputs is achievable in the interior of the distributed lossy compression rate region if the sources share non-trivial Gï¿½cs-Kï¿½rner common information.

@inproceedings{Vellambi2016,
author = {Vellambi, Badri N. and Kliewer, J\"org and Bloch, Matthieu R.},
title = {Lossy Compression with Near-uniform Encoder Outputs},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2016},
pages = {530-534},
month = jul,
doi = {10.1109/ISIT.2016.7541355},
groups = {Randomness processing},
keywords = {Decoding;Distortion;Electronic mail;Encoding;Monte Carlo methods;Receivers},
owner = {mattbloch},
timestamp = {2016.01.26}
}


20. K. S. K. Arumugam and M. R. Bloch, “Keyless Covert Communication over Multiple-Access Channels,” in Proc. of IEEE International Symposium on Information Theory, Barcelona, Spain, Jul. 2016, pp. 2229–2233.

We consider a scenario in which two legitimate transmitters attempt to communicate with a legitimate receiver over a discrete memoryless Multiple-Access Channel (MAC), while escaping detection from an adversary who observes their communication through another discrete memoryless MAC. If the MAC to the legitimate receiver is "better" than the one to the adversary, in a sense that we make precise, then the legitimate users can reliably communicate on the order of sqrtn bits per n channel uses with arbitrarily Low Probability of Detection (LPD) without using a secret key. We also identify the pre-constants of the scaling, which leads to a characterization of the covert capacity region.

@inproceedings{Arumugam2016,
author = {Arumugam, Keerthi Suria Kumar and Bloch, Matthieu R.},
title = {Keyless Covert Communication over Multiple-Access Channels},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2016},
pages = {2229-2233},
month = jul,
doi = {10.1109/ISIT.2016.7541695},
groups = {Steganography and covert communications},
owner = {mattbloch},
timestamp = {2016.01.26}
}


21. M. Tahmasbi and M. R. Bloch, “Second-Order Asymptotics of Covert Communications over Noisy Channels,” in Proc. of IEEE International Symposium on Information Theory, Barcelona, Spain, Jul. 2016, pp. 2224–2228.

We consider the problem of covert communication over noisy binary input Discrete Memoryless Channels (DMCs). Covertness is measured with respect to an adversary in terms of the divergence between the channel output distribution induced with and without communication. We characterize the exact second order asymptotics of the number of bits that can be reliably transmitted with a probability of error less than epsilon and a divergence less than delta. The main technical contribution of this paper is a detailed analysis of how to expurgate a random code while maintaining its channel resolvability properties.

@inproceedings{Tahmasbi2016,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R.},
title = {Second-Order Asymptotics of Covert Communications over Noisy Channels},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2016},
pages = {2224-2228},
month = jul,
doi = {10.1109/ISIT.2016.7541694},
groups = {Steganography and covert communications},
keywords = {Encoding;Monte Carlo methods;Noise measurement;Random variables;Reliability;Zinc},
owner = {mattbloch},
timestamp = {2016.01.26}
}


22. M. Le Treust and M. R. Bloch, “Empirical Coordination, State Masking and State Amplification: Core of the Decoder’s Knowledge,” in Proc. of IEEE International Symposium on Information Theory, Barcelona, Spain, Jul. 2016, pp. 895–899.

We revisit the problem of state masking and state amplification for state-dependent channel with causal state information at the encoder from the point of view of empirical coordination. Empirical coordination, which requires all sequences of symbols to be jointly typical for a target joint probability distribution, provides a unified perspective to simultaneously study state masking, state amplification, and capacity-distortion trade-off. Our main result is a characterization of the set of achievable rates, information leakages and joint distributions. We also discuss several specializations and extensions of the result, including the cases of zero message rate, without empirical coordination, strictly causal encoding, two-sided state information and noisy channel feedback. We introduce the notion of "core of the decoder’s knowledge," to capture what the decoder can infer about all the signals involved in the model.

@inproceedings{LeTreust2016,
author = {{Le Treust}, Mael and Bloch, Matthieu R.},
title = {Empirical Coordination, State Masking and State Amplification: Core of the Decoder's Knowledge},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2016},
pages = {895-899},
month = jul,
doi = {10.1109/ISIT.2016.7541428},
groups = {Coordination of networks},
keywords = {Channel coding;Decoding;Distortion;Probability distribution;Random variables;Causal Encoding;Empirical Coordination;Information Leakage;Noisy Channel Feedback;Shannon Theory;State Amplification;State Masking;State-Dependent Channel},
owner = {mattbloch},
timestamp = {2016.01.26}
}


23. B. N. Vellambi, J. Kliewer, and M. R. Bloch, “Strong coordination over a line when actions are Markovian,” in Proc. of Annual Conference on Information Science and Systems, Princeton, NJ, Mar. 2016, pp. 412–417.

We analyze the problem of strong coordination over a multi-hop line network when the actions to be generated by the nodes satisfy a Markov chain that is matched to the network topology. We devise and prove the optimality of two schemes that cover the portions of the capacity region corresponding to unlimited or no common randomness shared by all nodes.

@inproceedings{Vellambi2015b,
author = {Vellambi, B. N. and Kliewer, J. and Bloch, M. R.},
title = {Strong coordination over a line when actions are Markovian},
booktitle = {Proc. of Annual Conference on Information Science and Systems},
year = {2016},
pages = {412-417},
month = mar,
doi = {10.1109/CISS.2016.7460538},
groups = {Coordination of networks},
keywords = {Markov processes;random processes;telecommunication network topology;telecommunication transmission lines;Markov chain;capacity region;multihop line network;network topology;no common randomness;strong coordination problem;unlimited randomness;Strong coordination;channel resolvability;channel synthesis;line network},
owner = {mattbloch},
timestamp = {2015.12.15}
}


24. R. A. Chou and M. R. Bloch, “Using deterministic decisions for low-entropy bits in the encoding and decoding of polar codes,” in Proc. of 53rd Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2015, pp. 1380–1385.

We show how to replace some of the randomized decisions in the encoding and decoding of polar codes by deterministic decisions. Specifically, we prove that random decisions on low-entropy bits may be replaced by an argmax decision without any loss of performance. We illustrate the usefulness of this result in the case of polar coding for the Wyner-Ziv problem and for channel coding.

@inproceedings{Chou2015a,
author = {Chou, R. A. and Bloch, M. R.},
title = {Using deterministic decisions for low-entropy bits in the encoding and decoding of polar codes},
booktitle = {Proc. of 53rd Annual Allerton Conference on Communication, Control, and Computing},
year = {2015},
pages = {1380-1385},
month = sep,
doi = {10.1109/ALLERTON.2015.7447169},
groups = {Polar codes},
keywords = {channel coding;Wyner-Ziv problem;argmax decision;channel coding;deterministic decisions;low-entropy bits;polar codes;Channel coding;Computers;Couplings;Decoding;Distortion;Source coding},
owner = {mattbloch},
timestamp = {2015.07.07}
}


25. B. N. Vellambi, J. Kliewer, and M. Bloch, “Strong Coordination over Multi-hop Line Networks,” in Proc. of IEEE Information Theory Workshop, Jeju, Korea, Jul. 2015, pp. 192–196.

We analyze the problem of strong coordination over a multi-hop line network where the node initiating the coordination is a terminal network node. We provide a characterization of the capacity region when the initiating node possesses unlimited local randomness and intermediate nodes operate under a functional regime. In this regime, next-hop messages are created only using common randomness and previous-hop incoming messages, i.e., local randomness at intermediate nodes is only used for generating actions.

@inproceedings{Vellambi2015a,
author = {Vellambi, Badri N. and Kliewer, Joerg and Bloch, Matthieu},
title = {Strong Coordination over Multi-hop Line Networks},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2015},
pages = {192-196},
month = jul,
doi = {10.1109/ITWF.2015.7360761},
groups = {Coordination of networks},
howpublished = {accepted to \emph{IEEE Information Theory Workshop}},
keywords = {radio networks;capacity region;hop incoming messages;intermediate nodes;multihop line networks;next-hop messages;terminal network node;Conferences;Electronic mail;Information theory;Random variables;Relays;Spread spectrum communication;Yttrium},
owner = {mattbloch},
timestamp = {2015.05.25}
}


26. B. N. Vellambi, M. R. Bloch, R. A. Chou, and J. Kliewer, “Lossless and Lossy Source Compression with Near-Uniform Outputs: Is Common Randomness Always Required?,” in Proc. of IEEE International Symposium on Information Theory, Hong Kong, Jun. 2015, pp. 2171–2175.

It is known that a sub-linear rate of source-independent random seed (common randomness) can enable the construction of lossless compression codes whose output is nearly uniform under the variational distance (Chou-Bloch-ISIT’13). This work uses finite-blocklength techniques to present an alternate proof that for near-uniform lossless compression, the seed length has to grow strictly larger than n, where n represents the blocklength of the lossless compression code. In the lossy setting, we show the surprising result that a seed is not required to make the encoder output nearly uniform.

@inproceedings{Vellambi2015,
author = {Vellambi, Badri N. and Bloch, Matthieu R and Chou, R\'emi A and Kliewer, Joerg},
title = {Lossless and Lossy Source Compression with Near-Uniform Outputs: Is Common Randomness Always Required?},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2015},
pages = {2171--2175},
month = jun,
doi = {10.1109/ISIT.2015.7282840},
groups = {Randomness processing},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
keywords = {Decoding;Distortion;Encoding;Manganese;Random variables;Tin;Finite-blocklength techniques;Lossless coding;Rate-distortion;Source coding},
owner = {mattbloch},
timestamp = {2015.01.27}
}


27. R. A. Chou, M. R. Bloch, and J. Kliewer, “Polar Coding for Empirical and Strong Coordination via Distribution Approximation,” in Proc. of IEEE International Symposium on Information Theory, Hong Kong, Jun. 2015, pp. 1512–1516.

We design low-complexity polar codes for empirical and strong coordination in two-node network. Our constructions hinge on the observation that polar codes may be used to approximate distribution; which we leverage to prove that nested polar codes achieve the capacity region of empirical coordination and strong coordination.

@inproceedings{Chou2015,
author = {Chou, R\'emi A. and Bloch, Matthieu R and Kliewer, Joerg},
title = {Polar Coding for Empirical and Strong Coordination via Distribution Approximation},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2015},
pages = {1512--1516},
month = jun,
doi = {10.1109/ISIT.2015.7282708},
groups = {Polar codes, Coordination of networks},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
keywords = {Approximation methods;Convergence;Decoding;Encoding;Joints;Probability distribution;Random variables},
owner = {mattbloch},
timestamp = {2015.01.27}
}


28. M. R. Bloch, “A Channel Resolvability Perspective on Stealth Communications,” in Proc. of IEEE International Symposium on Information Theory, Hong Kong, Jun. 2015, pp. 2535–2539.

We analyze the problem of stealth communication and low probability of detection from the perspective of channel resolvability. We show that stealth communication over discrete memoryless channels and additive white Gaussian noise channels is possible without secret key as soon as the legitimate receiver’s channel is "better" than the warden’s channel, which generalizes previously known results to a much larger class of channels. The underlying technical problem that we solve is how to develop concentration inequalities for "low weight" sequences; the crux of our approach is to define modified "typical sets" that are amenable to concentration inequalities.

@inproceedings{Bloch2015,
author = {Bloch, Matthieu R},
title = {A Channel Resolvability Perspective on Stealth Communications},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2015},
pages = {2535--2539},
month = jun,
doi = {10.1109/ISIT.2015.7282913},
groups = {Steganography and covert communications},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
keywords = {AWGN channels;Memoryless systems;Noise measurement;Random variables;Reliability theory},
owner = {mattbloch},
timestamp = {2015.01.27}
}


29. R. A. Chou and M. R. Bloch, “Polar Coding for the Broadcast Channel with Confidential Messages,” in Proc. IEEE Information Theory Workshop, Jerusalem, Israel, Apr. 2015, pp. 1–5.

We develop a low-complexity and secrecy capacity achieving polar coding scheme for the discrete memoryless wiretap channel. Our scheme extends previous work by using a nearly optimal amount of uniform randomness in the stochastic encoder, and avoiding assumptions regarding the symmetry or degraded nature of the channels. The price paid for these extensions is that the encoder and decoder are required to share a secret seed of negligible size. We also highlight a close conceptual connection between the proposed polar coding scheme and a random binning proof of the secrecy capacity.

@inproceedings{Chou2014e,
author = {Chou, R\'emi A. and Bloch, Matthieu R},
title = {Polar Coding for the Broadcast Channel with Confidential Messages},
booktitle = {Proc. IEEE Information Theory Workshop},
year = {2015},
pages = {1-5},
month = apr,
doi = {10.1109/ITW.2015.7133142},
groups = {Wiretap codes, Polar codes},
howpublished = {accepted to \emph{IEEE Information Theory Workshop}},
keywords = {broadcast channels;channel capacity;channel coding;decoding;broadcast channel;channel symmetry;confidential messages;decoder;discrete memoryless wiretap channel;polar coding scheme;secrecy capacity;stochastic encoder;Channel coding;Decoding;Entropy;Joints;Parity check codes;Stochastic processes},
owner = {mattbloch},
timestamp = {2014.11.13}
}


30. R. A. Chou, M. R. Bloch, and J. Kliewer, “Low-Complexity Channel Resolvability Codes for the Symmetric Multiple-Access Channel,” in Proc. of IEEE Information Theory Workshop, Hobart, Tasmania, Nov. 2014, pp. 466–470.

@inproceedings{Chou2014,
author = {Chou, R\'emi A. and Bloch, Matthieu R and Kliewer, J\"org},
title = {Low-Complexity Channel Resolvability Codes for the Symmetric Multiple-Access Channel},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2014},
pages = {466--470},
month = nov,
doi = {10.1109/ITW.2014.6970875},
groups = {Randomness processing},
howpublished = {accepted to \emph{IEEE Information Theory Workhop}},
owner = {mattbloch},
timestamp = {2014.01.24}
}


31. M. R. Bloch and J. Kliewer, “Strong Coordination over a Three-Terminal Relay Network,” in Proc. of IEEE Information Theory Workshop, Hobart, Tasmania, Nov. 2014, pp. 646–650.

@inproceedings{Bloch2014a,
author = {Bloch, Matthieu R and Kliewer, Joerg},
title = {Strong Coordination over a Three-Terminal Relay Network},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2014},
pages = {646--650},
month = nov,
doi = {10.1109/ITW.2014.6970911},
groups = {Coordination of networks},
howpublished = {accepted to \emph{IEEE Information Theory Workshop}},
owner = {mattbloch},
timestamp = {2014.05.12}
}


32. R. A. Chou and M. R. Bloch, “Uniform Distributed Source Coding for the Multiple Access Wiretap Channel,” in Proc. of IEEE Conference on Communications and Network Security, San Francisco, CA, Oct. 2014, pp. 127–132.

@inproceedings{Chou2014c,
author = {Chou, Remi A. and Bloch, Matthieu R},
title = {Uniform Distributed Source Coding for the Multiple Access Wiretap Channel},
booktitle = {Proc. of IEEE Conference on Communications and Network Security},
year = {2014},
pages = {127--132},
month = oct,
doi = {10.1109/CNS.2014.6997477},
groups = {Wiretap channels},
howpublished = {accepted at \emph{IEEE Conference on Communications and Network Security: Wokshop on Physical-layer Methods for Wireless Security} (invited)},
owner = {mattbloch},
timestamp = {2014.07.07}
}


33. V. Y. F. Tan and M. R. Bloch, “Information spectrum approach to strong converse theorems for degraded wiretap channels,” in Proc. of 52nd Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2014, pp. 747–754.

@inproceedings{Tan2014,
author = {Tan, Vincent Y. F. and Bloch, Matthieu R.},
title = {Information spectrum approach to strong converse theorems for degraded wiretap channels},
booktitle = {Proc. of 52nd Annual Allerton Conference on Communication, Control, and Computing},
year = {2014},
pages = {747-754},
month = sep,
doi = {10.1109/ALLERTON.2014.7028529},
eprint = {1406.6758},
groups = {Wiretap channels},
keywords = {Capacity planning;Error probability;Manganese;Measurement;Random variables;Security;Zinc},
owner = {mattbloch},
timestamp = {2014.06.15}
}


34. N. Li et al., “Ultrafast Random Bit Generation Based on the Chaotic Dynamics of a Semiconductor Laser,” in Proc. of CLEO, San Jose, CA, Jun. 2014, pp. 1–2.

We achieve physical random bit generation (RBG) that does not exceed the limit set by information theory via extracting 4 bits per sample or keep 55 bits per sample, leading to faster physical-based pseudo RBG.

@inproceedings{Li2014,
author = {Li, Nianqiang and Kim, Byungchil and Chizhevsky, V. N. and Locquet, Alexandre and Bloch, Matthieu and Citrin, David and Pan, Wei},
title = {Ultrafast Random Bit Generation Based on the Chaotic Dynamics of a Semiconductor Laser},
booktitle = {Proc. of CLEO},
year = {2014},
pages = {1--2},
month = jun,
doi = {10.1364/CLEO_AT.2014.JTh2A.102},
groups = {Physical random number generation},
journal = {{CLEO}: 2014},
keywords = {Chaos; Semiconductor lasers; Instabilities and chaos}
}


35. J. J. Boutros, V. Dedeoglu, and M. R. Bloch, “The Anti-Diversity Concept for Secure Communication on a Two-Link Compound Channel,” in Proc. of International Zurich Seminar on Communications, Zurich, Switzerland, Feb. 2014.

@inproceedings{Boutros2013,
author = {Boutros, Joseph J. and Dedeoglu, Volkan and Bloch, Matthieu R.},
title = {The Anti-Diversity Concept for Secure Communication on a Two-Link Compound Channel},
booktitle = {Proc. of International Zurich Seminar on Communications},
year = {2014},
month = feb,
doi = {10.3929/ethz-a-010095293},
groups = {Wiretap codes},
howpublished = {accepted to \emph{2014 International Zurich Seminar}},
owner = {mattbloch},
timestamp = {2013.10.24}
}


36. R. A. Chou and M. R. Bloch, “Secret-Key Generation with Arbitrarily Varying Eavesdropper’s Channel,” in Proc. of Global Conference on Signal and Information Processing, Austin, TX, Sep. 2013, pp. 277–280.

@inproceedings{Chou2013c,
author = {Chou, R\'emi A. and Bloch, Matthieu R},
title = {Secret-Key Generation with Arbitrarily Varying Eavesdropper's Channel},
booktitle = {Proc. of Global Conference on Signal and Information Processing},
year = {2013},
pages = {277--280},
month = sep,
doi = {10.1109/GlobalSIP.2013.6736869},
groups = {Secret key agreement},
owner = {mattbloch},
timestamp = {2013.10.21}
}


37. M. R. Bloch and J. Kliewer, “Strong coordination over a line network,” in Proc. IEEE International Symposium on Information Theory, Istanbul, Turkey, Jul. 2013, pp. 2319–2323.

@inproceedings{Bloch2013a,
author = {Bloch, Matthieu R. and Kliewer, Joerg},
title = {Strong coordination over a line network},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2013},
pages = {2319-2323},
month = jul,
doi = {10.1109/ISIT.2013.6620640},
eprint = {1305.5992},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
issn = {2157-8095},
owner = {mattbloch},
quality = {1},
timestamp = {2013.01.21}
}


38. R. A. Chou and M. R. Bloch, “Data compression with nearly uniform ouput,” in Proc. IEEE International Symposium on Information Theory, Istanbul, Turkey, Jul. 2013, pp. 1979–1983.

For any lossless fixed-length compression scheme operating at the optimal coding rate, it is known that the encoder output is not uniform in variational distance, which yet might be desirable in some security schemes. In the case of independent and identically distributed (i.i.d.) sources, uniformity in divergence might be achieved if a uniformly distributed sequence, called seed, of length dn negligible compared to the message length n, is shared between the encoder and the decoder. We show that the optimal scaling of dn that jointly ensures an optimal coding rate and a uniform encoder output in divergence, is roughly on the order of sqrt(n). We also develop a near optimal achievability scheme using invertible extractors.

@inproceedings{Chou2013,
author = {Chou, Remi A. and Bloch, Matthieu R.},
title = {Data compression with nearly uniform ouput},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2013},
pages = {1979-1983},
month = jul,
doi = {10.1109/ISIT.2013.6620572},
file = {:Users/mattbloch/Documents/Publications/2013-Chou-ISIT.pdf:PDF},
groups = {Randomness processing},
issn = {2157-8095}
}


39. C. Ling, L. Luzzi, and M. R. Bloch, “Secret key generation from Gaussian sources using lattice hashing,” in Proc. IEEE International Symposium on Information Theory, Istanbul, Turkey, Jul. 2013, pp. 2621–2625.

@inproceedings{Lin2013,
author = {Ling, Cong and Luzzi, Laura and Bloch, Matthieu R.},
title = {Secret key generation from Gaussian sources using lattice hashing},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2013},
pages = {2621-2625},
month = jul,
doi = {10.1109/ISIT.2013.6620701},
eprint = {1306.5299},
file = {:Users/mattbloch/Documents/Publications/2013-Ling-ISIT.pdf:PDF},
groups = {Secret key agreement},
issn = {2157-8095},
keywords = {Encoding;Error probability;Lattices;Quantization (signal);Vectors;Zinc},
owner = {mattbloch},
quality = {1},
timestamp = {2013.01.21}
}


40. A. J. Pierrot and M. R. Bloch, “Joint Channel Intrinsic Randomness and Channel Resolvability,” in Proc. of Information Theory Workshop, Sevilla, Spain, Apr. 2013, pp. 1–5.

This paper investigates the separation of channel intrinsic randomness and channel resolvability. We derive joint exponents, which are compared to the tandem exponents obtained with a separate approach. We prove at once, in a simple manner, achievability results for channel intrinsic randomness, random number generation, and channel resolvability. We also provide converse results in different special settings.

@inproceedings{Pierrot2013b,
author = {Pierrot, Alexandre J. and Bloch, Matthieu R.},
title = {Joint Channel Intrinsic Randomness and Channel Resolvability},
booktitle = {Proc. of Information Theory Workshop},
year = {2013},
pages = {1-5},
month = apr,
doi = {10.1109/ITW.2013.6691334},
howpublished = {accepted to \emph{IEEE Information Theory Workshop}},
owner = {mbloch},
timestamp = {2013.04.17}
}


41. F. Renna et al., “Low-power secret key agreement over OFDM,” in Proc. of the 2nd ACM workshop on Hot topics on wireless network security and privacy, Budaptest, Hungary, Apr. 2013, pp. 43–48.

Information-theoretic secret-key agreement is perhaps the most practically feasible mechanism that provides unconditional security at the physical layer to date. In this paper, we consider the problem of secret-key agreement by sharing randomness at low power over an orthogonal frequency division multiplexing (OFDM) link, in the presence of an eavesdropper. The low power assumption greatly simplifies the design of the randomness sharing scheme, even in a fading channel scenario. We assess the performance of the proposed system in terms of secrecy key rate and show that a practical approach to key sharing is obtained by using low-density parity check (LDPC) codes for information reconciliation. Numerical results confirm the merits of the proposed approach as a feasible and practical solution. Moreover, the outage formulation allows to implement secret-key agreement even when only statistical knowledge of the eavesdropper channel is available.

@inproceedings{Renna2013,
author = {Renna, Francesco and Laurenti, Nicola and Tomasin, Stefano and Baldi, Marco and Maturo, Nicola and Bianchi, Marco and Chiaraluce, Franco and Bloch, Matthieu},
title = {Low-power secret key agreement over {OFDM}},
booktitle = {Proc. of the 2nd ACM workshop on Hot topics on wireless network security and privacy},
year = {2013},
pages = {43--48},
month = apr,
doi = {10.1145/2463183.2463194},
file = {:2013-Renna-HotWiSec.pdf:PDF},
groups = {Secret key agreement},
howpublished = {accepted to the \emph{Second ACM Workshop on Hot Topics on Wireless Network Security and Privacy}},
owner = {mattbloch},
quality = {1},
timestamp = {2013.01.25}
}


42. A. J. Pierrot, R. A. Chou, and M. R. Bloch, “Experimental Aspects of Secret-Key Generation in Indoor Wireless Environments,” in Proc. of Signal IEEE 4th Workshop on Signal Processing Advances in Wireless Communications, Apr. 2013.

This paper proposes a proof-of-principle design of a secret key generation system along with the desirable secrecy analysis to guarantee information-theoretic security. We conduct physical experiments on programmable radios in an indoor environment to analyze the statistical characteristics of the induced source that we employ to generate secret keys. We also provide a generic security analysis of the system, and we give an estimate of the achievable secret key rates for a target information leakage in the finite block-length regime.

@inproceedings{Pierrot2013a,
author = {Pierrot, Alexandre J. and Chou, R\'emi A. and Bloch, Matthieu R.},
title = {Experimental Aspects of Secret-Key Generation in Indoor Wireless Environments},
booktitle = {Proc. of Signal IEEE 4th Workshop on Signal Processing Advances in Wireless Communications},
year = {2013},
month = apr,
doi = {10.1109/SPAWC.2013.6612134},
file = {:../Publications/2013-Pierrot-SPAWC.pdf:PDF},
groups = {Experimental systems},
howpublished = {accepted to \emph{IEEE Workshop on Signal Processing Advances in Wireless Communications}},
owner = {mattbloch},
timestamp = {2013.02.13}
}


43. R. A. Chou, M. R. Bloch, and E. Abbe, “Polar Coding for Secret-Key Generation,” in Proc. of Information Theory Workshop, Sevilla, Spain, Apr. 2013, pp. 1–5.

Practical implementations of secret-key generation are often based on sequential strategies, which handle reliability and secrecy in two successive steps, called reconciliation and privacy amplification. In this paper, we propose an alternative scheme based on polar coding that jointly deals with reliability and secrecy. We study a binary degraded symmetric discrete memoryless source model with uniform marginals, and assume one-way rate-limited public communication between two legitimate users. Specifically, we propose secret-key capacity-achieving polar coding schemes, in which users rely on pre-shared secret seed of negligible rate. For the model studied, we thus provide the first example of low-complexity secret-key capacity-achieving scheme that handles vector quantization, for rate-limited public communication. Furthermore, we provide examples for which no seed is required.

@inproceedings{Chou2013a,
author = {Chou, R\'emi A. and Bloch, Matthieu R. and Abbe, Emmanuel},
title = {Polar Coding for Secret-Key Generation},
booktitle = {Proc. of Information Theory Workshop},
year = {2013},
pages = {1-5},
month = apr,
doi = {10.1109/ITW.2013.6691225},
eprint = {1305.4746},
groups = {Secret key agreement, Polar codes},
howpublished = {accepted to \emph{IEEE Information Theory Workshop}},
owner = {mattbloch},
timestamp = {2013.03.07}
}


44. M. R. Bloch, L. Luzzi, and J. Kliewer, “Strong Coordination with Polar Codes,” in Proc. of 50th Allerton Conference on Communication, Control, and Computing, Monticello, IL, Oct. 2012, pp. 565–571.

In this paper, we design explicit codes for strong coordination in two-node networks. Specifically, we consider a two-node network in which the action imposed by nature is binary and uniform, and the action to coordinate is obtained via a symmetric discrete memoryless channel. By observing that polar codes are useful for channel resolvability over binary symmetric channels, we prove that nested polar codes achieve a subset of the strong coordination capacity region, and therefore provide a constructive and low complexity solution for strong coordination.

@inproceedings{Bloch2012a,
author = {Bloch, Matthieu R. and Luzzi, Laura and Kliewer, Joerg},
title = {{S}trong Coordination with Polar Codes},
booktitle = {Proc. of 50th Allerton Conference on Communication, Control, and Computing},
year = {2012},
pages = {565-571},
month = oct,
arxiv = {1210.2159},
doi = {10.1109/Allerton.2012.6483268},
file = {:2012-Bloch-Allerton.pdf:PDF},
groups = {Coordination of networks, Polar codes},
howpublished = {accepted to \emph{50th Allerton Conference on Communication, Control, and Computing}},
owner = {mattbloch},
timestamp = {2012.07.15}
}


45. A. J. Pierrot and M. R. Bloch, “LDPC-based coded cooperative jamming codes,” in Proc. of IEEE Information Theory Workshop, Lausanne, Switzerland, Sep. 2012, pp. 462–466.

We present a practical coded cooperative jamming scheme for the problem of secure communications over the two-way wiretap channel. We design low-density parity-check (LDPC) based codes whose codewords interfere at the eavesdropper’s terminal, thus providing secrecy. We show that our scheme can guarantee low information leakage rate, and we assess its precise performance for classical and spatially coupled LDPC codes.

@inproceedings{Pierrot2012,
author = {Pierrot, Alexandre J. and Bloch, Matthieu R.},
title = {{LDPC}-based coded cooperative jamming codes},
booktitle = {Proc. of IEEE Information Theory Workshop},
year = {2012},
pages = {462--466},
month = sep,
doi = {10.1109/ITW.2012.6404716},
file = {:2012-Pierrot-ITW.pdf:PDF},
groups = {Wiretap codes},
howpublished = {accepted at \emph{IEEE Information Theory Workshop}},
owner = {mattbloch},
timestamp = {2012.03.14}
}


46. R. A. Chou and M. R. Bloch, “One-way rate-limited sequential key-distillation,” in Proc. IEEE International Symp.Information Theory, Cambridge, MA, Jul. 2012, pp. 1777–1781.

We study the problem of key-distillation for a source model, with a one-way and rate-limited public communication between two legitimate users. Although, the secret-key capacity is already known, we provide an alternative achievability scheme, that directly translates into practical designs. We consider a sequential key-distillation strategy, which consists of a reconciliation phase followed by a privacy amplification phase performed with extractors. We determine the reconciliation capacity and show that, for a degraded source, such a sequential strategy leads to an optimal key-distillation strategy that achieves the secret-key capacity. We illustrate our results in the case of a binary source model.

@inproceedings{Chou2012,
author = {Chou, Remi A. and Bloch, Matthieu R.},
title = {One-way rate-limited sequential key-distillation},
booktitle = {Proc. IEEE International Symp.Information Theory},
year = {2012},
pages = {1777--1781},
month = jul,
doi = {10.1109/ISIT.2012.6283584},
file = {:2012-Chou-ISIT.pdf:PDF},
groups = {Secret key agreement},
owner = {mattbloch},
timestamp = {2012.08.30}
}


47. M. R. Bloch and J. Kliewer, “On secure communication with constrained randomization,” in Proc. IEEE International Symp.Information Theory, Cambridge, MA, Jul. 2012, pp. 1172–1176.

In this paper, we investigate how constraints on the randomization in the encoding process affect the secrecy rates achievable over wiretap channels. In particular, we characterize the secrecy capacity with a rate-limited local source of randomness and a less capable eavesdropper’s channel, which shows that limited rate incurs a secrecy rate penalty but does not preclude secrecy. We also show that secure communication is possible when randomizing with a non-uniform source of randomness, which suggests the possibility of designing robust coding schemes.

@inproceedings{Bloch2012,
author = {Bloch, Matthieu R. and Kliewer, Joerg},
title = {On secure communication with constrained randomization},
booktitle = {Proc. IEEE International Symp.Information Theory},
year = {2012},
pages = {1172--1176},
month = jul,
doi = {10.1109/ISIT.2012.6283039},
file = {:2012-Bloch-ISIT.pdf:PDF},
groups = {Wiretap channels},
owner = {mattbloch},
timestamp = {2012.08.30}
}


48. M. R. Bloch, “Achieving Secrecy: capacity vs. Resolvability,” in Proc. of IEEE International Symposium on Information Theory, Saint Petersburg, Russia, Aug. 2011, pp. 632–636.

@inproceedings{Bloch2011a,
author = {Bloch, Matthieu R.},
title = {{A}chieving Secrecy: capacity vs. Resolvability},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2011},
pages = {632--636},
month = aug,
doi = {10.1109/ISIT.2011.6034207},
file = {:2011-Bloch-ISIT.pdf:PDF},
groups = {Wiretap channels},
howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}},
owner = {mattbloch},
timestamp = {2011.02.22}
}


49. F. Renna, M. Bloch, and N. Laurenti, “Semi-Blind Key-Agreement over MIMO Fading Channels,” in Proc. IEEE International Conference on Communications, Kyoto, Japan, Jun. 2011, pp. 1–6.

We analyze the fundamental limits of secret-<span class=’snippet’>key</span> <span class=’snippet’>agreement</span> <span class=’snippet’>over</span> <span class=’snippet’>MIMO</span> quasi-static <span class=’snippet’>fading</span> <span class=’snippet’>channels</span>. In the low-power and high-power regimes, we establish closed-form expressions for secret-<span class=’snippet’>key</span> capacity. In the low-power regime, we show that the optimal signaling strategy is independent of the eavesdropper’s <span class=’snippet’>fading</span> realization. The low-power secret-<span class=’snippet’>key</span> capacity is achieved by transmitting along the direction corresponding to the maximal eigenvalue of the legitimate <span class=’snippet’>channel</span>. By combining this signaling strategy with reconciliation and privacy amplification, one obtains a <span class=’snippet’>semi</span>-<span class=’snippet’>blind</span> <span class=’snippet’>key</span>-distillation strategy in which the knowledge of the eavesdropper’s <span class=’snippet’>fading</span> is required for privacy amplification alone.

@inproceedings{Renna2011,
author = {Renna, Francesco and Bloch, Matthieu and Laurenti, Nicola},
title = {{S}emi-Blind Key-Agreement over {MIMO} Fading Channels},
booktitle = {Proc. IEEE International Conference on Communications},
year = {2011},
pages = {1--6},
month = jun,
doi = {10.1109/icc.2011.5963438},
file = {:2011-Renna-ICC.pdf:PDF},
groups = {Secret key agreement},
owner = {mattbloch},
timestamp = {2011.08.17}
}


50. L. Luzzi and M. R. Bloch, “Capacity-based random codes cannot achieve strong secrecy over symmetric wiretap channels,” in Proc. of the 5th International ICST Conference on Performance Evaluation Methodologies and Tools, Cachan, France, May 2011, pp. 641–647.

@inproceedings{Luzzi2011,
author = {Luzzi, Laura and Bloch, Matthieu R.},
title = {{C}apacity-based random codes cannot achieve strong secrecy over symmetric wiretap channels},
booktitle = {Proc. of the 5th International ICST Conference on Performance Evaluation Methodologies and Tools},
year = {2011},
pages = {641--647},
month = may,
note = {(invited)},
groups = {Wiretap channels},
howpublished = {accepted at \emph{SecureNets 2011}},
owner = {mattbloch},
timestamp = {2011.04.16},
url = {http://dl.acm.org/citation.cfm?id=2151688.2151767}
}


51. F. Renna, M. Bloch, and N. Laurenti, “Semi-Blind Key-Agreement over MIMO Quasi-Static Channels,” in Proc. of 2011 NEWCOM/COST Joint Workshop, Paris, France, Mar. 2011, pp. 1–6.

@inproceedings{Renna2011a,
author = {Renna, Francesco and Bloch, Matthieu and Laurenti, Nicola},
title = {{S}emi-Blind Key-Agreement over {MIMO} Quasi-Static Channels},
booktitle = {Proc. of 2011 NEWCOM/COST Joint Workshop},
year = {2011},
pages = {1--6},
month = mar,
groups = {Secret key agreement},
howpublished = {accepted to \emph{NEWCOM++ / COST 2100 Joint workshop}},
owner = {mattbloch},
timestamp = {2011.01.17}
}


52. A. T. Suresh, A. Subramanian, A. Thangaraj, M. Bloch, and S. McLaughlin, “Strong Secrecy for Erasure Wiretap Channels,” in Proc. IEEE Information Theory Workshop, Dublin, Ireland, Sep. 2010.

@inproceedings{Suresh2010,
author = {Suresh, Ananda T. and Subramanian, Arunkumar and Thangaraj, Andrew and Bloch, Matthieu and McLaughlin, Steven},
title = {{S}trong Secrecy for Erasure Wiretap Channels},
booktitle = {Proc. IEEE Information Theory Workshop},
year = {2010},
month = sep,
citeseerurl = {1004.5540},
doi = {10.1109/CIG.2010.5592770},
groups = {Wiretap codes},
howpublished = {accepted at the IEEE Information Theory Workshop, Dublin},
owner = {matthieu},
timestamp = {2010.03.30}
}


53. A. Subramanian, A. T. Suresh, A. Thangaraj, M. Bloch, and S. McLaughlin, “Strong and Weak Secrecy in Wiretap Channels,” in Proc. of 6th International Symposium on Turbo Codes and Iterative Information Processing, Brest, France, Sep. 2010, pp. 30–34.

In the wiretap channel model, symbols transmitted through a main channel to a legitimate receiver are observed by an eavesdropper across a wiretapper’s channel. The goal of coding for wiretap channels is to facilitate error-free decoding across the main channel, while ensuring zero information transfer across the wiretapper’s channel. Strong secrecy requires the total information transfer to the eavesdropper to tend to zero, while weak secrecy requires the per-symbol information transfer to go to zero. In this paper, we will consider coding methods for binary wiretap channels with a noiseless main channel and a BEC or a BSC wiretapper’s channel. We will provide conditions and codes that achieve strong and weak secrecy for the BEC case. For the BSC case, we will discuss some existing coding methods and develop additional criteria for secrecy.

@inproceedings{Subramanian2010,
author = {Subramanian, Arunkumar and Suresh, Ananda T. and Thangaraj, Andrew and Bloch, Matthieu and McLaughlin, Steven},
title = {{S}trong and Weak Secrecy in Wiretap Channels},
booktitle = {Proc. of 6th International Symposium on Turbo Codes and Iterative Information Processing},
year = {2010},
pages = {30 - 34},
month = sep,
note = {(invited)},
doi = {10.1109/ISTC.2010.5613867},
groups = {Wiretap codes},
howpublished = {accepted at 6th International Symposium on Turbo Codes and Iterative Information Processing},
owner = {matthieu},
timestamp = {2010.07.11}
}


54. M. Bloch, “Channel Intrinsic Randomness,” in Proc. of IEEE International Symposium on Information Theory, Austin, TX, Jun. 2010, pp. 2607–2611.

@inproceedings{Bloch2010b,
author = {Bloch, Matthieu},
title = {{C}hannel Intrinsic Randomness},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2010},
pages = {2607--2611},
month = jun,
doi = {10.1109/ISIT.2010.5513744},
file = {:2010-Bloch-ISIT.pdf:PDF},
groups = {Randomness processing},
howpublished = {accepted at IEEE International Symposium on Information Theory 2010},
owner = {matthieu},
timestamp = {2009.12.30}
}


55. J. P. Vilela, M. Bloch, J. Barros, and S. W. McLaughlin, “Friendly Jamming for Wireless Secrecy,” in Proc. of IEEE International Conference on Communications, Cape Town, South Africa, May 2010, pp. 1550–3607.

@inproceedings{Vilela2010,
author = {Vilela, Joao Paulo and Bloch, Matthieu and Barros, Joao and McLaughlin, Steven W.},
title = {{F}riendly Jamming for Wireless Secrecy},
booktitle = {Proc. of IEEE International Conference on Communications},
year = {2010},
pages = {1550-3607},
address = {Cape Town, South Africa},
month = may,
doi = {10.1109/ICC.2010.5502606},
groups = {Wiretap channels},
howpublished = {To appear in proceeding of IEEE International Conference on Communications},
owner = {matthieu},
timestamp = {2008.12.19}
}


56. M. Rodrigues, A. Somekh-Baruch, and M. Bloch, “On Gaussian Wiretap Channels with Arbitrary Inputs,” in Proc. of European Wireless, Lucca, Italy, Apr. 2010, pp. 774–781.

This paper investigates the secrecy capacity of the Gaussian wiretap channel with M-PAM inputs, by capitalizing on the relationship between mutual information and minimum mean squared error (MMSE). In particular, we establish optimality conditions for both the M-PAM input power and the M-PAM input distribution, which we specialize to the asymptotic low-power and high-power regimes. By using the properties of the MMSE to establish sufficient conditions for the uniqueness of the solution of some of the underlying non-convex optimization problems, we also propose efficient algorithms to compute the optimal solutions. Interestingly, we show that with M-PAM inputs it is sub-optimal to use all the available power for some range of parameters - this is in sharp contrast to standard Gaussian channels. We also extend the results to the parallel Gaussian wiretap channel with M-PAM inputs. We put forth a mercury-waterfilling interpretation of the optimal power allocation procedure for parallel Gaussian wiretap channels which generalizes the conventional mercury-waterfilling interpretation for parallel Gaussian channels, with the mercury level amending the base level to account for both the non-Gaussianess of the input and the secrecy constraint.

@inproceedings{Rodrigues2010,
author = {Rodrigues, Miguel and Somekh-Baruch, Anelia and Bloch, Matthieu},
title = {{O}n {G}aussian Wiretap Channels with Arbitrary Inputs},
booktitle = {Proc. of European Wireless},
year = {2010},
pages = {774--781},
month = apr,
doi = {10.1109/EW.2010.5483475},
file = {:2010-Rodrigues-EW.pdf:PDF},
groups = {Wiretap channels},
howpublished = {accepted at European Wireless 2010},
keywords = {Gaussian wiretap channels;M-PAM inputs;minimum mean squared error;mutual information;mean square error methods;radio networks;telecommunication channels;},
owner = {matthieu},
timestamp = {2009.11.10}
}


57. E. MolavianJazi, M. Bloch, and J. N. Laneman, “Arbitrary Jamming Can Preclude Secure Communications,” in Proc. 47th Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2009, pp. 1069–1075.

@inproceedings{MolavianJazi2009,
author = {MolavianJazi, Ebrahim and Bloch, Matthieu and Laneman, J. Nicholas},
title = {{A}rbitrary Jamming Can Preclude Secure Communications},
booktitle = {Proc. 47th Annual Allerton Conference on Communication, Control, and Computing},
year = {2009},
pages = {1069--1075},
month = sep,
doi = {10.1109/ALLERTON.2009.5394876},
file = {:2009-MolavianJazi-Allerton.pdf:PDF},
howpublished = {accepted at 47th Allerton Conference on Communications, Control, and Computing},
owner = {matthieu},
timestamp = {2009.07.09}
}


58. M. Bloch, “Channel Scrambling for Secrecy,” in Proc. of IEEE International Symposium on Information Theory, Seoul, Korea, Jul. 2009, pp. 2452–2456.

@inproceedings{Bloch2009a,
author = {Bloch, Matthieu},
title = {{C}hannel Scrambling for Secrecy},
booktitle = {Proc. of IEEE International Symposium on Information Theory},
year = {2009},
pages = {2452--2456},
month = jul,
doi = {10.1109/ISIT.2009.5206058},
file = {:2009-Bloch-ISIT.pdf:PDF},
groups = {Wiretap channels},
howpublished = {accepted at the 2009 IEEE International Symposium on Information Theory},
owner = {matthieu},
timestamp = {2008.12.19}
}


59. B. P. Dunn, M. Bloch, and J. N. Laneman, “Secure bits through queues,” in Proc. IEEE Information Theory Workshop on Networking and Information Theory, Volos, Greece, Jun. 2009, pp. 37–41.

We investigate the idea of providing information-theoretic security at the network and data link layers by exploiting the timing information resulting from queuing of packets between a source, an intended receiver, and other users in a network. Specifically, we consider the secure transmission of messages by encoding them onto the interarrival timing of packets that enter parallel queues. By leveraging recent results on the secrecy capacity of arbitrary wiretap channels, achievable secrecy rates are obtained. We also show that equivalent secrecy rates can be achieved using a deterministic encoding strategy, which provides an example contrasting the fact that for many memoryless channels a stochastic encoder is required to achieve non-zero secrecy rates.

@inproceedings{Dunn2009,
author = {Dunn, Brian P. and Bloch, Matthieu and Laneman, J. Nicholas},
title = {{S}ecure bits through queues},
booktitle = {Proc. IEEE Information Theory Workshop on Networking and Information Theory},
year = {2009},
pages = {37--41},
month = jun,
doi = {10.1109/ITWNIT.2009.5158537},
file = {:2009-Dunn-ITW.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2009.07.09}
}


60. M. Bloch and J. N. Laneman, “Information-Spectrum Methods for Information-Theoretic Security,” in Proc. Information Theory and Applications Workshop, San Diego, CA, Feb. 2009, pp. 23–28.

@inproceedings{Bloch2009,
author = {Bloch, Matthieu and Laneman, J. Nicholas},
title = {{I}nformation-Spectrum Methods for Information-Theoretic Security},
booktitle = {Proc. Information Theory and Applications Workshop},
year = {2009},
pages = {23--28},
month = feb,
note = {(invited)},
doi = {10.1109/ITA.2009.5044918},
file = {:2009-Bloch-ITA.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2008.11.19}
}


61. M. Bloch and J. N. Laneman, “On the Secrecy Capacity of Arbitrary Wiretap Channels,” in Proceedings of 46th Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2008, pp. 818–825.

@inproceedings{Bloch2008e,
author = {Bloch, Matthieu and Laneman, J. Nicholas},
title = {{O}n the Secrecy Capacity of Arbitrary Wiretap Channels},
booktitle = {Proceedings of 46th Allerton Conference on Communication, Control, and Computing},
year = {2008},
pages = {818--825},
month = sep,
doi = {10.1109/ALLERTON.2008.4797642},
file = {:2008-Bloch-Allerton.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2008.08.04}
}


62. J. Barros and M. Bloch, “Strong Secrecy for Wireless Channels,” in Information Theoretic Security, Calgary, Canada, Aug. 2008, pp. 40–53.

@inproceedings{Barros2008,
author = {Barros, Jo{\~a}o and Bloch, Matthieu},
title = {{S}trong Secrecy for Wireless Channels},
booktitle = {Information Theoretic Security},
year = {2008},
series = {Lecture Notes in Computer Science},
pages = {40-53},
month = aug,
publisher = {Springer Berlin / Heidelberg},
note = {(invited)},
doi = {10.1007/978-3-540-85093-9_5},
groups = {Wiretap channels, Wireless security},
owner = {matthieu},
timestamp = {2008.06.20}
}


63. S. Fossier et al., “Quantum Key Distribution over 25 km Using a Fiber Setup Based on Continuous Variables,” in Proc. of CLEO/QELS, San Jose, CA, May 2008, pp. 1–2.

@inproceedings{Fossier2008,
author = {Fossier, Simon and Lodewyck, J. and Diamanti, E. and Bloch, M. and Debuisschert, T. and Tualle-Brouri, R. and Grangier, P.},
title = {{Q}uantum Key Distribution over 25 km Using a Fiber Setup Based on Continuous Variables},
booktitle = {Proc. of CLEO/QELS},
year = {2008},
pages = {1--2},
month = may,
comment = {http://www.opticsinfobase.org/abstract.cfm?URI=QELS-2008-QWE2},
doi = {10.1109/QELS.2008.4553262},
file = {:2008-Fossier-CLEO.pdf:PDF},
groups = {Quantum key distribution},
owner = {matthieu},
timestamp = {2008.04.22}
}


64. M. Bloch and A. Thangaraj, “Confidential Messages to a Cooperative Relay,” in Proc. of the IEEE Information Theory Workshop, Porto, Portugal, May 2008, pp. 154–158.

@inproceedings{Bloch2008b,
author = {Bloch, Matthieu and Thangaraj, Andrew},
title = {{C}onfidential Messages to a Cooperative Relay},
booktitle = {Proc. of the IEEE Information Theory Workshop},
year = {2008},
pages = {154--158},
month = may,
doi = {10.1109/ITW.2008.4578641},
file = {:2008-Bloch-ITW.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2007.12.16}
}


65. M. Bloch, R. Narasimha, and S. W. McLaughlin, “Client-Server Architecture Design based on Wiretap Codes,” in Proc of the 2008 International Zurich Seminar on Communications, Zurich, Switzerland, Mar. 2008, pp. 44–47.

We propose a method to design attack-resistant client-server architectures based on wiretap codes. We show that by appropriately spreading messages across different packets a client-server architecture under active attack can be modeled as a passive wiretap channel. The secrecy capacity of this equivalent wiretap channel is then used as an optimization metric to limit the impact of the attacks.

@inproceedings{Bloch2008,
author = {Bloch, Matthieu and Narasimha, Rajesh and McLaughlin, Steven W.},
title = {{C}lient-Server Architecture Design based on Wiretap Codes},
booktitle = {Proc of the 2008 International Zurich Seminar on Communications},
year = {2008},
pages = {44--47},
month = mar,
doi = {10.1109/IZS.2008.4497272},
file = {:2008-Bloch-IZS.pdf:PDF},
groups = {Wiretap channels},
owner = {matthieu},
timestamp = {2007.12.16}
}


66. E. Diamanti et al., “Implementation of an all-fiber continuous variables quantum key distribution system,” in International Conference on Quantum Information Processing and Communication, Barcelona, Spain, Oct. 2007.

@inproceedings{Diamanti2007,
author = {Diamanti, Eleni and Fossier, Simon and Lodewyck, J\'erome and Bloch, Matthieu and Garcia-Patron, Raul and Karpov, Evgueni and Debuisschert, Thierry and Cerf, Nicolas J. and Tualle-Brouri, Rosa and McLaughlin, Steven W. and Grangier, Philippe},
title = {{I}mplementation of an all-fiber continuous variables quantum key distribution system},
booktitle = {International Conference on Quantum Information Processing and Communication},
year = {2007},
month = oct,
groups = {Quantum key distribution},
owner = {matthieu},
timestamp = {2008.01.14}
}


67. M. Bloch, J. Barros, and S. W. McLaughlin, “Practical Information-Theoretic Commitment,” in Proc. 45th Allerton Conference on Communication Control and Computing, Monticello, IL, Sep. 2007, pp. 1035–1039.

@inproceedings{Bloch2007d,
author = {Bloch, Matthieu and Barros, Joao and McLaughlin, Steven W.},
title = {{P}ractical Information-Theoretic Commitment},
booktitle = {Proc. 45th Allerton Conference on Communication Control and Computing},
year = {2007},
pages = {1035--1039},
month = sep,
comment = {Cited 1 time 1. A Practical Scheme for String Commitment based on the Gaussian Channel, Frederique Oggier and Kirill Morozo , IEEE Information Theory Workshop, 2008},
groups = {Cryptographic primitives},
owner = {Matthieu},
timestamp = {2006.11.15}
}


68. J. Lodewyck et al., “Quantum key distribution device with coherent states,” in Proc. of SPIE Optics East, Boston, MA, USA, Sep. 2007, vol. 6780, pp. 67800Z/1–14.

@inproceedings{Lodewyck2007b,
author = {Lodewyck, J. and Bloch, M. and Garcia-Patron, R. and Fossier, S. and Karpov, E. and Diamanti, E. and Debuisschert, T. and Cerf, N. J. and Tualle-Brouri, R. and McLaughlin, S. W. and Grangier, P.},
title = {{Q}uantum key distribution device with coherent states},
booktitle = {Proc. of SPIE Optics East},
year = {2007},
volume = {6780},
pages = {67800Z/1-14},
month = sep,
note = {(invited)},
doi = {10.1117/12.736855},
file = {:2007-Lodewyck-SPIEeast.pdf:PDF},
groups = {Quantum key distribution},
owner = {matthieu},
timestamp = {2007.10.01}
}


69. J. Lodewyck et al., “Distribution quantique de clé a 25 km au moyen d’un dispositif fibré utilisant des variables continues,” in 10eme Colloque sur les Lasers et l’Optique Quantique, Grenoble, France, Jul. 2007.

@inproceedings{Lodewyck2007a,
author = {Lodewyck, J\'erome and Bloch, Matthieu and Fossier, Simon and Diamanti, Eleni and Debuisschert, Thierry and Tualle-Brouri, Rosa and Grangier, Philippe},
title = {{D}istribution quantique de cl\'e a 25 km au moyen d'un dispositif fibr\'e utilisant des variables continues},
booktitle = {10eme Colloque sur les Lasers et l'Optique Quantique},
year = {2007},
month = jul,
doi = {10.1051/anphys:2008033},
file = {:2007-Lodewyck-COLOQ.pdf:PDF},
groups = {Quantum key distribution},
owner = {matthieu},
timestamp = {2007.10.01}
}


70. S. Kaimalettu, A. Thangaraj, M. Bloch, and S. W. McLaughlin, “Constellation Shaping using LDPC Codes,” in Proc. IEEE International Symposium on Information Theory, Nice, France, Jun. 2007, pp. 2366–2370.

It is well-known that a Gaussian source distribution is required for maximum information transfer across a Gaussian channel. In a coded modulation system an equiprobable symbol constellation loses at most 1.53 dB when compared to a Gaussian source. To bridge this shaping gap, a code can be used to make the source distribution more Gaussian over an expanded constellation that results in lower average transmitted energy. Trellis shaping uses convolutional codes and the Viterbi algorithm for minimizing the transmitted energy. In this work, we propose trellis shaping using low-density parity-check codes as the shaping codes. We show that the 2-state min-sum algorithm over the Tanner graph can be used to efficiently implement the energy minimization. This is a more than 4-fold decrease in complexity over 4-state convolutional code-based trellis shaping. Using one of our simple shaping codes, we have observed a shaping gain of up to 0.65 dB (with CER = 1.26; PAPR = 3.86) (as compared with CER=1.41 and PAPR=3.3 for convolutional-code based trellis shaping with similar shaping gain). This encouraging result indicates that more complex LDPC-based approaches will do even better. We also present simulation results to show that constellation shaping provides similar gains over wireless channels under slow fading conditions.

@inproceedings{Kaimalettu2007,
author = {Kaimalettu, Sunil and Thangaraj, Andrew and Bloch, Matthieu and McLaughlin, Steven W.},
title = {{C}onstellation Shaping using {LDPC} Codes},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2007},
pages = {2366--2370},
month = jun,
doi = {10.1109/ISIT.2007.4557573},
file = {:Users/matthieu/Documents/publications/2007-Kaimalettu-ISIT.pdf:PDF;2007-Kaimalettu-ISIT.pdf:2007-Kaimalettu-ISIT.pdf:PDF},
keywords = {LDPC},
owner = {matthieu},
timestamp = {2007.04.03}
}


71. M. Bloch, J. Barros, M. R. D. Rodrigues, and S. W. McLaughlin, “Information Theoretic Security for Wireless Channels - Theory and Practice,” in Proc. 2007 Information Theory and Application Workshop, San Diego, CA, USA, Feb. 2007.

@inproceedings{Bloch2007c,
author = {Bloch, Matthieu and Barros, Jo{\~a}o and Rodrigues, Miguel R. D. and McLaughlin, Steven W.},
title = {{I}nformation Theoretic Security for Wireless Channels - Theory and Practice},
booktitle = {Proc. 2007 Information Theory and Application Workshop},
year = {2007},
address = {San Diego, CA, USA},
month = feb,
note = {(invited)},
comment = {Cited 2 times 1. On the Secrecy Capabilities of ITU Channels, Ye, Chunxuan; Reznik, Alex; Sternburg, Gregory; Shah, Yogendra; Vehicular Technology Conference, 2007 2. Secure Nested Codes for Type II Wiretap Channels, Liu, R.; Liand, Y.; Poor, H. V. & Spasojevi\'c, P., 2007 IEEE Information Theory Workshop, 2007 3. Securing Media Hotspots, Biri, A; Ahmad, A; Affifi H, Wireless Telecomunications Symposium, 2008. WTS 2008},
groups = {Wireless security},
owner = {Matthieu},
timestamp = {2007.07.17}
}


72. M. Bloch, J. Barros, M. R. D. Rodrigues, and S. W. McLaughlin, “LDPC-based Secure Wireless Communication with Imperfect Knowledge of the Eavesdropper’s Channels,” in Proc. IEEE Information Theory Workshop, Chengdu, China, Oct. 2006, pp. 155–159.

@inproceedings{Bloch2006c,
author = {Bloch, Matthieu and Barros, Jo{\~a}o and Rodrigues, Miguel R. D. and McLaughlin, Steven W.},
title = {{LDPC}-based Secure Wireless Communication with Imperfect Knowledge of the Eavesdropper's Channels},
booktitle = {Proc. IEEE Information Theory Workshop},
year = {2006},
pages = {155-159},
month = oct,
doi = {10.1109/ITW2.2006.323778},
file = {:Users/matthieu/Documents/publications/2006-Bloch-ITW-China.pdf:PDF;2006-Bloch-ITW(2).pdf:2006-Bloch-ITW(2).pdf:PDF},
groups = {Wireless security},
owner = {Matthieu},
timestamp = {2006.11.15}
}


73. S. Donnet, A. Thangaraj, M. Bloch, J. Cussey, J.-M. Merolla, and L. Larger, “Cryptanalysis of Y-00 under Heterodyne Measurement and Fast Correlation Attack,” in Proc. European Conference on Optical Communication, Cannes, France, Sep. 2006, pp. 1–2.

@inproceedings{Donnet2006a,
author = {Donnet, St\'ephane and Thangaraj, Andrew and Bloch, Matthieu and Cussey, Johann and Merolla, Jean-Marc and Larger, Laurent},
title = {{C}ryptanalysis of {Y}-00 under Heterodyne Measurement and Fast Correlation Attack},
booktitle = {Proc. European Conference on Optical Communication},
year = {2006},
pages = {1--2},
month = sep,
doi = {10.1109/ECOC.2006.4801097},
groups = {Quantum key distribution},
owner = {Matthieu},
timestamp = {2006.11.15}
}


74. M. Bloch, J. Barros, M. R. D. Rodrigues, and S. W. McLaughlin, “An Opportunistic Physical-Layer Approach to Secure Wireless Communications,” in Proc. 44th Allerton Conference on Communication Control and Computing, Monticello, IL, Sep. 2006, pp. 849–854.

@inproceedings{Bloch2006b,
author = {Bloch, Matthieu and Barros, Jo{\~a}o and Rodrigues, Miguel R. D. and McLaughlin, Steven W.},
title = {{A}n Opportunistic Physical-Layer Approach to Secure Wireless Communications},
booktitle = {Proc. 44th Allerton Conference on Communication Control and Computing},
year = {2006},
pages = {849--854},
month = sep,
comment = {Cited 1 time 1. Secure Communication over Fading Channels , Liang, Y.; Poor, H. V. & (Shitz), S. S., 2008 (CHECK IEEE TRANS IT)},
file = {2006-Bloch-Allerton.pdf:2006-Bloch-Allerton.pdf:PDF},
groups = {Wireless security},
owner = {matthieu},
timestamp = {2007.08.10}
}


75. M. Bloch, A. Thangaraj, S. W. McLaughlin, and J.-M. Merolla, “LDPC-based Secret Key Agreement over the Gaussian wiretap channel,” in Proc. IEEE International Symposium on Information Theory, Seattle, USA, Jul. 2006, pp. 1179–1183.

This paper investigates a practical secret key agreement protocol over the Gaussian wire-tap channel. The protocol is based on an efficient information reconciliation method which allows two parties having access to correlated continuous random variables to agree on a common bit string.We describe an explicit reconciliation method based on LDPC codes optimized with EXIT charts and density evolution. When used in conjunction with existing privacy amplification techniques our method allows secret key agreement over the Gaussian wire-tap channel close to the secrecy capacity.

@inproceedings{Bloch2006a,
author = {Bloch, Matthieu and Thangaraj, Andrew and McLaughlin, Steven W. and Merolla, Jean-Marc},
title = {{LDPC}-based Secret Key Agreement over the {G}aussian wiretap channel},
booktitle = {Proc. IEEE International Symposium on Information Theory},
year = {2006},
pages = {1179-1183},
month = jul,
comment = {Cited 2 times 1. On the Possibility of Key Agreement Using Variable Directional Antenna, Imai, H.; Kobara, K. & Morozov, K., 1st Joint Workshop on Information Security, 2006 2. Secure Nested Codes for Type II Wiretap Channels, Liu, R.; Liand, Y.; Poor, H. V. & Spasojevi\'c, P., 2007 IEEE Information Theory Workshop, 2007},
doi = {10.1109/ISIT.2006.261991},
file = {:Users/matthieu/Documents/publications/2006-Bloch-ISIT.pdf:PDF;2006-Bloch-ISIT.pdf:2006-Bloch-ISIT.pdf:PDF},
groups = {Secret key agreement},
keywords = {LDPC, wire-tap channel},
owner = {Matthieu},
timestamp = {2006.11.15}
}


76. M. Bloch, A. Thangaraj, S. W. McLaughlin, and J.-M. Merolla, “LDPC-based Gaussian Key Reconciliation,” in Proc. IEEE Information Theory Workshop, Punta del Este, Uruguay, Mar. 2006, pp. 116–120.

We propose a new information reconciliation method which allows two parties sharing continuous random variables to agree on a common bit string. We show that existing coded modulation techniques can be adapted for reconciliation and give an explicit code construction based on LDPC codes in the case of Gaussian variables. Simulations show that our method achieves higher efficiency than previously reported results.

@inproceedings{Bloch2006,
author = {Bloch, Matthieu and Thangaraj, Andrew and McLaughlin, Steven W. and Merolla, {Jean}-{Marc}},
title = {{LDPC}-based {G}aussian Key Reconciliation},
booktitle = {Proc. IEEE Information Theory Workshop},
year = {2006},
pages = {116-120},
address = {Punta del Este, Uruguay},
month = mar,
note = {arXiv:cs.IT/0509041},
citeseerurl = {cs.IT/0509041},
comment = {Cited 2 times 1. Secrecy Capacity of Wireless Channels, Barros, J. & Rodrigues, M. R. D., IEEE International Symposium on Information Theory, 2006 2. Tight bound on coherent states quantum key distribution with heterodyne detection, Lodewyck, J. & Grangier, P., Physical Review A, 2007, 76, 022332/1-8 Preprint cited 4 times 1. Controlling excess noise in fiber-optics continuous-variable quantum key distribution, Lodewyck, J.; Debuisschert, T.; Tualle-Brouri, R. & Grangier, P., Physical Review A, 2005, 72, 050303/1-4 2. Optimality of Gaussian Attacks in Continuous-Variable Quantum Cryptography, Navascues, M.; Grosshans, F. & Acin, A., Physical Review Letters, 2006, 97, 190502/1-4 3. From quantum cloning to quantum key distribution with continuous variables: a review, Cerf, N. J. & Grangier, P., JOSA B, 2007, 24, 324-334 4. Experimental Implementation of Non-Gaussian Attacks on a Continuous-Variable Quantum-Key-Distribution System, Lodewyck, J.; Debuisschert, T.; Garcia-Patron, R.; Tualle-Brouri, R.; Cerf, N. J. & Grangier, P., Physical Review Letters, 2007, 98, 030503/1-4},
doi = {10.1109/ITW.2006.1633793},
file = {:Users/matthieu/Documents/publications/2006-Bloch-ITW-Uruguay.pdf:PDF;2006-Bloch-ITW.pdf:2006-Bloch-ITW.pdf:PDF},
groups = {Reconciliation algorithms, Secret key agreement},
keywords = {LDPC, continuous variables iterative decoding},
owner = {Matthieu},
timestamp = {2006.11.15}
}


77. J. Cussey, M. Bloch, A. Thangaraj, J.-M. Merolla, and S. W. McLaughlin, “Integrated Direct-Modulation Based Quantum Cryptography System,” in Proc. Optical Network and Technologies, Pisa, Italy, Oct. 2004, pp. 390–395.

@inproceedings{Cussey2004a,
author = {Cussey, Johann and Bloch, Matthieu and Thangaraj, Andrew and Merolla, Jean-Marc and McLaughlin, Steven W.},
title = {{I}ntegrated Direct-Modulation Based Quantum Cryptography System},
booktitle = {Proc. Optical Network and Technologies},
year = {2004},
series = {IFIP International Federation for Information Processing},
pages = {390--395},
month = oct,
organization = {IFIP},
doi = {10.1007/0-387-23178-1_49},
groups = {Quantum key distribution},
owner = {Matthieu},
timestamp = {2006.12.14}
}


78. J. Cussey, M. Bloch, A. Thangaraj, J.-M. Merolla, and S. W. McLaughlin, “Direct-Modulation Scheme for Free-Space Quantum Cryptography,” in Proc. European Conference on Optical Communication, Stockholm, Sweden, Sep. 2004.

@inproceedings{Cussey2004,
author = {Cussey, Johann and Bloch, Matthieu and Thangaraj, Andrew and Merolla, Jean-Marc and McLaughlin, Steven W.},