Security through the Lens of Information Asymmetry

Award information

Abstract

The needs of future networks beyond 5G and Internet of Things call for a comprehensive and inclusive approach to security. By harnessing the imperfections of communication channels, physical-layer security integrates security concerns into the design of communication systems with benefits such as energy efficiency and simplified key management; physical-layer security often imposes requirements, however, which has impeded its practical adoption and deployment. Furthermore, in some applications where physical-layer security is uniquely suitable and no obvious cryptographic solution exists, such as situations requiring covertness, results to date have been disappointing in terms of predicted data transmission speeds. This project addresses these two points. The outcomes of this project can ensure secure wireless communications in future networks with minimal performance impact.

The first thrust of this project brings a new perspective to the study of cooperative security through the lens of information asymmetry against adversaries. This part of the project aims to elucidate how cooperation can provide knowledge to one user about the variations in the channel induced by the signaling of another in a manner that creates new and hitherto unforeseen advantages over an adversary. The second thrust of this project explores the benefits of information asymmetry for covert communications, including the role of channel state knowledge, which is foreseen as a key mechanism to not only circumvent the square-root law of covert communication but also to alleviat the need for a shared secret key. The impact of different-quality channel states being available at different nodes will be studied.

Publications

1. T. Erdoğan, T. Kann, A. Nosratinia, and M. R. Bloch, “Covert Communication over Physically Degraded Alarm Two-Way Channels.” submitted from 2024 IEEE International Symposium on Information Theory, Jan. 2024.

   @misc{Erdogan2023Covert, author = {Erdo\u{g}an, Tuna and Kann, Tyler and Nosratinia, Aria and Bloch, Matthieu R.}, howpublished = {submitted from \emph{2024 IEEE International Symposium on Information Theory}}, month = jan, title = {Covert Communication over Physically Degraded Alarm Two-Way Channels}, year = {2024}, groups = {NSF1955401} }

2. L. Luzzi, C. Ling, and M. R. Bloch, “Optimal rate-limited secret key generation from Gaussian sources using lattices,” IEEE Transactions on Information Theory, vol. 69, no. 8, pp. 4944–4960, Aug. 2023.

   We propose a lattice-based scheme for secret key generation from Gaussian sources in the presence of an eavesdropper, and show that it achieves the strong secret key capacity in the case of degraded source models, as well as the optimal secret key / public communication rate trade-off. The key ingredients of our scheme are a lattice extractor to extract the channel intrinsic randomness, based on the notion of flatness factor, together with a randomized lattice quantization technique to quantize the continuous source. Compared to previous works, we introduce two new notions of flatness factor based on L1 distance and KL divergence, respectively, which are of independent interest. We prove the existence of secrecy-good lattices under L1 distance and KL divergence, whose L1 and KL flatness factors vanish for volume-to-noise ratios up to 2πe. This improves upon the volume-to-noise ratio threshold 2π of the L∞ flatness factor.

   @article{Luzzi2022Secret, author = {Luzzi, Laura and Ling, Cong and Bloch, Matthieu R.}, journal = {IEEE Transactions on Information Theory}, title = {Optimal rate-limited secret key generation from Gaussian sources using lattices}, year = {2023}, month = aug, number = {8}, pages = {4944-4960}, volume = {69}, doi = {10.1109/TIT.2023.3266033}, eprint = {2206.10443}, file = {:2023-Luzzi-IEEETransIT-Optimal Rate-Limited Secret Key Generation From Gaussian Sources Using Lattices.pdf:PDF}, groups = {NSF1955401, NSF2148400}, howpublished = {accepted to \emph{IEEE Transactions on Information Theory}} }

3. M.-C. Chang and M. R. Bloch, “Distributed Stochastic Bandits with Corrupted and Defective Input Commands,” in Proc. of IEEE International Symposium on Information Theory, Taipei, Taiwan, Jun. 2023, pp. 1318–1323.

   We analyze a distributed stochastic bandit model in which an agent controls multiple independent stochastic bandit machines. At each time step, the agent selects several machines for parallel exploitation but the arm pulled by each machine may differ from the command received either randomly (defective command) or adversarially (corrupted command). Machines that faithfully execute commands are called honest. We study situations in which the number of honest machines is either known or unknown and define appropriate notions of regret. With at least one honest machine and a known number of honest bandits, we provide a simple algorithm that achieves \tilde O\left( n^1/2 \right) regrets when commands are corrupted. Lower bounds on regret established by drawing connections to the problem of "low probability of detection," show the near optimality of the regret achieved by the algorithms.

   @inproceedings{Chang2023Distributed, author = {Chang, Meng-Che and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Distributed Stochastic Bandits with Corrupted and Defective Input Commands}, year = {2023}, address = {Taipei, Taiwan}, month = jun, pages = {1318-1323}, doi = {10.1109/ISIT54713.2023.10206787}, file = {:2023-Chang-ISIT-Distributed Stochastic Bandits with Corrupted and Defective Input Commands.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{2023 IEEE International Symposium on Information Theory}} }

4. M.-C. Chang, S.-Y. Wang, T. Erdoğan, and M. R. Bloch, “Rate and Detection-Error Exponent Tradeoff for Joint Communication and Sensing of Fixed Channel States,” IEEE Journal on Selected Areas in Information Theory, vol. 4, pp. 245–259, May 2023.

   We study the information-theoretic limits of joint communication and sensing when the sensing task is modeled as the estimation of a discrete channel state fixed during the transmission of an entire codeword. This setting captures scenarios in which the time scale over which sensing happens is significantly slower than the time scale over which symbol transmission occurs. The tradeoff between communication and sensing then takes the form of a tradeoff region between the rate of reliable communication and the state detection-error exponent. We investigate such tradeoffs for both mono-static and bi-static scenarios, in which the sensing task is performed at the transmitter or receiver, respectively. In the mono-static case, we develop an exact characterization of the tradeoff in open-loop, when the sensing is not used to assist the communication. We also show the strict improvement brought by a closed-loop operation, in which the sensing informs the communication. In the bi-static case, we develop an achievable tradeoff region that highlights the fundamentally different nature of the bi-static scenario. Specifically, the rate of communication plays a key role in the characterization of the tradeoff and we show how joint strategies, which simultaneously estimate message and state, outperform successive strategies, which only estimate the state after decoding the transmitted message.

   @article{Chang2022Ratea, author = {Chang, Meng-Che and Wang, Shi-Yuan and Erdo\u{g}an, Tuna and Bloch, Matthieu R.}, journal = {IEEE Journal on Selected Areas in Information Theory}, title = {Rate and Detection-Error Exponent Tradeoff for Joint Communication and Sensing of Fixed Channel States}, year = {2023}, month = may, pages = {245-259}, volume = {4}, doi = {10.1109/JSAIT.2023.3275877}, eprint = {2210.07963}, groups = {NSF2148400, NSF1955401}, howpublished = {accepted to \emph{IEEE Journal on Selected Areas in Information Theory}} }

5. O. Günlü, M. R. Bloch, R. F. Schaefer, and A. Yener, “Secure Integrated Sensing and Communication,” IEEE Journal on Selected Areas in Information Theory, vol. 4, pp. 40–53, May 2023.

   This work considers the problem of mitigating information leakage between communication and sensing in systems jointly performing both operations. Specifically, a discrete memoryless state-dependent broadcast channel model is studied in which (i) the presence of feedback enables a transmitter to convey information, while simultaneously performing channel state estimation; (ii) one of the receivers is treated as an eavesdropper whose state should be estimated but which should remain oblivious to part of the transmitted information. The model abstracts the challenges behind security for joint communication and sensing if one views the channel state as a sensitive attribute, e.g., location. For independent and identically distributed states, perfect output feedback, and when part of the transmitted message should be kept secret, a partial characterization of the secrecy-distortion region is developed. The characterization is exact when the broadcast channel is either physically-degraded or reversely-physically-degraded. The partial characterization is also extended to the situation in which the entire transmitted message should be kept secret. The benefits of a joint approach compared to separation-based secure communication and state-sensing methods are illustrated with binary joint communication and sensing models.

   @article{Guenlue2022SecureJSAIT, author = {G\"unl\"u, Onur and Bloch, Matthieu R. and Schaefer, Rafael F. and Yener, Aylin}, journal = {IEEE Journal on Selected Areas in Information Theory}, title = {Secure Integrated Sensing and Communication}, year = {2023}, month = may, pages = {40-53}, volume = {4}, doi = {10.1109/JSAIT.2023.3275048}, eprint = {2303.11350}, file = {:2023-Gunlu-JSAIT-Secure Integrated Sensing and Communication.pdf:PDF}, groups = {NSF1955401, NSF2148400}, howpublished = {accepted to \emph{IEEE Journal on Special Areas in Information Theory}} }

6. R. A. Chou and M. R. Bloch, “Retractable Commitment,” in Proc. of IEEE Information Theory Workshop, Saint-Malo, France, Apr. 2023, pp. 260–265.

   Consider a commitment protocol between two parties, Alice and Bob, in which Alice may (i) commit to a message using a non-redundant discrete memoryless channel whose outputs are observed by Bob; and (ii) later reveal her committed message to Bob who must decide whether Alice is revealing the message she actually committed to. A commitment protocol should meet three standard requirements: concealment, bindingness, and soundness, to ensure that no party may act dishonestly. Our objective is to study whether one can enforce a fourth requirement that would allow Alice to retract a commitment before the reveal phase starts without Bob detecting that she ever participated in the commit phase of the protocol. We positively answer this question and characterize the commitment capacity for such a setting by relying on tools developed for covert communication.

   @inproceedings{Chou2023Retractable, author = {Chou, R\'emi A. and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE Information Theory Workshop}, title = {Retractable Commitment}, year = {2023}, address = {Saint-Malo, France}, month = apr, pages = {260--265}, doi = {10.1109/ITW55543.2023.10161683}, file = {:2023-Chou-ITW-Retractable Commitment over Noisy Channels.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Information Theory Workshop}} }

7. O. Günlü, M. R. Bloch, and R. Schaeffer, “Private Remote Sources for Secure Multi-Function Computation,” IEEE Transactions on Information Theory, vol. 10, no. 68, pp. 1557–9654, Oct. 2022.

   We consider a distributed function computation problem in which parties observing noisy versions of a remote source facilitate the computation of a function of their observations at a fusion center through public communication. The distributed function computation is subject to constraints, including not only reliability and storage but also privacy and secrecy. Specifically, 1) the remote source should remain private from an eavesdropper and the fusion center, measured in terms of the information leaked about the remote source; 2) the function computed should remain secret from the eavesdropper, measured in terms of the information leaked about the arguments of the function, to ensure secrecy regardless of the exact function used. We derive the exact rate regions for lossless and lossy single-function computation and illustrate the lossy single-function computation rate region for an information bottleneck example, in which the optimal auxiliary random variables are characterized for binary-input symmetric-output channels. We extend the approach to lossless and lossy asynchronous multiple-function computations with joint secrecy and privacy constraints, in which case inner and outer bounds for the rate regions differing only in the Markov chain conditions imposed are characterized.

   @article{Guenlue2021a, author = {G\"unl\"u, Onur and Bloch, Matthieu R and Schaeffer, Rafael}, journal = {IEEE Transactions on Information Theory}, title = {Private Remote Sources for Secure Multi-Function Computation}, year = {2022}, month = oct, number = {68}, pages = {1557-9654}, volume = {10}, doi = {10.1109/TIT.2022.3182416}, eprint = {2106.09485}, file = {:2022-Gunlu-IEEETransIT-Private Remote Sources for Secure Multi-Function Computation.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Transactions on Information Theory}} }

8. M.-C. Chang, S.-Y. Wang, and M. R. Bloch, “Controlled Sensing with Corrupted Commands,” in Proc. of 58th Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sep. 2022.

   We consider a non-adaptive controlled sensing sce-nario in which the actions of the decision maker are corrupted by an adversary. The objective of the decision maker is to either detect the presence of the corruption or make a correct decision. Accordingly, the performance of a controlled sensing strategy is measured in terms of the error probability when there is no adversary, denoted PE,0 , and the error probability when an adversary is present, denoted PE,1 . Our main result is Stein-lemma like characterization of the optimal achievable error exponent of PE,0 subject to a constraint on PE,1 . We also illustrate the result with numerical examples.

   @inproceedings{Chang2022Controlled, author = {Chang, Meng-Che and Wang, Shi-Yuan and Bloch, Matthieu R.}, booktitle = {Proc. of 58th Annual Allerton Conference on Communication, Control, and Computing}, title = {Controlled Sensing with Corrupted Commands}, year = {2022}, address = {Monticello, IL}, month = sep, doi = {10.1109/Allerton49937.2022.9929364}, file = {:2022-Chang-Allerton-Controlled Sensing with Corrupted Commands.pdf:PDF}, groups = {NSF1955401, NSF1910859}, howpublished = {accepted to \emph{Allerton conference}} }

9. H. Zivari-Fard, M. Bloch, and A. Nosratinia, “Keyless Covert Communication via Channel State Information,” IEEE Transactions on Information Theory, vol. 68, no. 8, pp. 5440–5474, Aug. 2022.

   We consider the problem of covert communication over a state-dependent channel when the channel state is available either non-causally, causally, or strictly causally, either at the transmitter alone or at both transmitter and receiver. Covert communication with respect to an adversary, called "warden," is one in which, despite communication over the channel, the warden’s observation remains indistinguishable from an output induced by innocent channel-input symbols. Covert communication involves fooling an adversary in part by a proliferation of codebooks; for reliable decoding at the legitimate receiver, the codebook uncertainty is typically removed via a shared secret key that is unavailable to the warden. In contrast to previous work, we do not assume the availability of a shared key at the transmitter and legitimate receiver. Instead, shared randomness is extracted from the channel state in a manner that keeps it secret from the warden, despite the influence of the channel state on the warden’s output. When channel state is available at the transmitter and receiver, we derive the covert capacity region. When channel state is only available at the transmitter, we derive inner and outer bounds on the covert capacity. We provide examples for which the covert capacity is positive with knowledge of channel state information but is zero without it.

   @article{ZivariFard2020, author = {Zivari-Fard, Hassan and Bloch, Matthieu and Nosratinia, Aria}, journal = {IEEE Transactions on Information Theory}, title = {Keyless Covert Communication via Channel State Information}, year = {2022}, month = aug, number = {8}, pages = {5440-5474}, volume = {68}, doi = {10.1109/TIT.2021.3135291}, file = {:2022-ZivariFard-IEEETransIT-Keyless_Covert_Communication_via_Channel_State_Information.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Transactions on Information Theory}} }

10. M.-C. Chang and M. R. Bloch, “Covert Best Arm Identification of Stochastic Bandits,” in Proc. of IEEE International Symposium on Information Theory, Helsinki, Finland, Jun. 2022, pp. 324–329.

    We study the covert best arm identification problem in which an agent tries to identify the best arm while escaping detection from an adversary. Specifically, the agent should identify the best arm of the bandit with accuracy higher than a predefined requirement as soon as possible and, simultaneously, the adversary’s observations induced by pulling effective arms should remain indistinguishable from the observations obtained when no effective arm is pulled. Our main result is the characterization of the exponent γ, which captures the asymptotic exponential decrease of the confidence level with the square-root of the averaged stopping time.

    @inproceedings{Chang2022Covert, author = {Chang, Meng-Che and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Covert Best Arm Identification of Stochastic Bandits}, year = {2022}, address = {Helsinki, Finland}, month = jun, pages = {324-329}, doi = {10.1109/ISIT50566.2022.9834559}, file = {:2022-Chang-ISIT-Covert Best Arm Identification of Stochastic Bandits.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

11. O. Günlü, M. R. Bloch, R. Schaefer, and A. Yener, “Secure Joint Communication and Sensing,” in Proc. of IEEE International Symposium on Information Theory, Helskinki, Finland, Jun. 2022, pp. 844–849.

    @inproceedings{Guenlue2022Secure, author = {G\"unl\"u, Onur and Bloch, Matthieu R. and Schaefer, Rafael and Yener, Aylin}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Secure Joint Communication and Sensing}, year = {2022}, address = {Helskinki, Finland}, month = jun, pages = {844-849}, doi = {10.1109/ISIT50566.2022.9834748}, file = {:2022-Gunlu-ISIT-Secure_Joint_Communication_and_Sensing.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

12. H. Zivari-Fard, M. R. Bloch, and A. Nosratinia, “Covert Communication in the Presence of an Uninformed, Informed, and Coordinated Jammer,” in Proc. of IEEE International Symposium on Information Theory, Helsinki, Finland, Jun. 2022.

    This paper investigates covert communication in the presence of a cooperative jammer. Covert communication refers to the inability of an adversary to distinguish data transmission from a so-called innocent symbol at the input. We consider three related problems: (1) a jammer without direct communication or coordination with the transmitter, (2) a jammer that cribs the output of the transmitter, and (3) a jammer that is able to coordinate with the transmitter via a secret key that is also shared with the legitimate receiver. For each model, we derive inner and outer bounds on the capacity region that are tight in some special cases. Unlike prior results in the literature, the jammer in our model does not have access to unlimited local randomness. In fact, uncovering the fundamental interplay between the covert communication rate, local randomness, and secret key rate, is one of the distinctions and contributions of the present work. In the context of a few specific channels, we calculate achievable covert rates to illuminate our results.

    @inproceedings{ZivariFard2022Covert, author = {Zivari-Fard, Hassan and Bloch, Matthieu R. and Nosratinia, Aria}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Covert Communication in the Presence of an Uninformed, Informed, and Coordinated Jammer}, year = {2022}, address = {Helsinki, Finland}, month = jun, doi = {10.1109/ISIT50566.2022.9834682}, file = {:2022-ZivariFard-ISIT-Covert Communication in the Presence of an Uninformed Informed and Coordinated Jammer.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

13. M.-C. Chang, T. Erdoğan, S.-Y. Wang, and M. R. Bloch, “Rate and Detection Error-Exponent Tradeoffs of Joint Communication and Sensing,” in Proc. of IEEE International Symposium on Joint Communications & Sensing, Vienna, Austria, Mar. 2022, pp. 1–6.

    We consider a communication model in which a transmitter attempts to communicate with a receiver over a state-dependent channel and simultaneously estimate the state using strictly causal noisy state observations. Motivated by joint communication and sensing scenarios in which the physical phenomenon of interest for sensing evolves at a much slower rate than the rate of communication, the state is assumed to remain constant over the duration of the transmission. We derive a complete characterization of the optimal asymptotic trade-off between communication rate and detection-error exponent when coding strategies are open loop. We also show that closed-loop strategies result in strict improvements of the trade-offs.

    @inproceedings{Chang2022Rate, author = {Chang, Meng-Che and Erdo\u{g}an, Tuna and Wang, Shi-Yuan and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Joint Communications \& Sensing}, title = {Rate and Detection Error-Exponent Tradeoffs of Joint Communication and Sensing}, year = {2022}, address = {Vienna, Austria}, month = mar, pages = {1--6}, doi = {10.1109/JCS54387.2022.9743498}, file = {:2022-Chang-ISJCS-Rate and Detection Error-Exponent Tradeoffs of Joint Communication and Sensing.pdf:PDF}, groups = {Joint communication and sensing, NSF1955401, NSF1910859}, howpublished = {accepted to the \emph{IEEE International Hybrid Symposium on Joint Communications \& Sensing}} }

14. M.-C. Chang and M. R. Bloch, “Covert Sequential Hypothesis Testing,” in Proc. of IEEE Information Theory Workshop, Oct. 2021, pp. 1–6.

    @inproceedings{Chang2021a, author = {Chang, Meng-Che and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE Information Theory Workshop}, title = {Covert Sequential Hypothesis Testing}, year = {2021}, month = oct, pages = {1-6}, doi = {10.1109/ITW48936.2021.9611391}, file = {:2021-Chang-ITW-Covert sequential hypothesis testing.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Information Theory Workshop}} }

15. H. ZivariFard, M. R. Bloch, and A. Nosratinia, “Covert Communication via Non-Causal Cribbing from a Cooperative Jammer,” in Proc. of IEEE International Symposium on Information Theory, Jul. 2021, pp. 202–207.

    We consider the problem of covert communication in the presence of a cooperative jammer. Covert communication refers to communication that is undetectable by an adversary, i.e., a scenario in which, despite ongoing communication, the output distribution observed by an adversary called the “warden” is indistinguishable from the distribution that would have been induced by an innocent channel-input symbol. It is known that in general, a transmitter and a receiver can communicate only O(n−−√) covert bits over n channel uses, i.e., zero rate. This paper shows that a cooperative jammer can facilitate the communication of positive covert rates, subject to the transmitter having non-causal access to the jammer signal. An achievable rate region is calculated that highlights the relation between the covert communication rate, jammer’s randomness (expressed as a rate), and rate of a secret key shared between transmitter and receiver.

    @inproceedings{ZivariFard2021, author = {ZivariFard, Hassan and Bloch, Matthieu R. and Nosratinia, Aria}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Covert Communication via Non-Causal Cribbing from a Cooperative Jammer}, year = {2021}, month = jul, pages = {202-207}, doi = {10.1109/ISIT45174.2021.9517883}, file = {:2021-ZivariFard-ISIT-Covert Communication via Non-Causal Cribbing from a Cooperative Jammer.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

16. O. Günlü, M. Bloch, and R. F. Schaefer, “Secure Multi-Function Computation with Private Remote Sources,” in Proc. of IEEE International Symposium on Information Theory, Jul. 2021, pp. 1403–1408.

    We consider a distributed function computation problem in which parties observing noisy versions of a remote source facilitate the computation of a function of their observations at a fusion center through public communication. The distributed function computation is subject to constraints, including not only reliability and storage but also privacy and secrecy. Specifically, 1) the remote source should remain private from an eavesdropper and the fusion center, measured in terms of the information leaked about the remote source; 2) the function computed should remain secret from the eavesdropper, measured in terms of the information leaked about the arguments of the function, to ensure secrecy regardless of the exact function used. We derive the exact rate regions for lossless and lossy single-function computation and illustrate the lossy single-function computation rate region for an information bottleneck example, in which the optimal auxiliary random variables are characterized for binary input symmetric output channels. We extend the approach to lossless and lossy asynchronous multiple-function computations with joint secrecy and privacy constraints, in which case inner and outer bounds for the rate regions differing only in the Markov chain conditions imposed are characterized.

    @inproceedings{Guenlue2021, author = {G\"unl\"u, Onur and Bloch, Matthieu and Schaefer, Rafael F.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Secure Multi-Function Computation with Private Remote Sources}, year = {2021}, month = jul, pages = {1403-1408}, doi = {10.1109/ISIT45174.2021.9518019}, file = {:2021-Gunlu-ISIT-Secure Multi-Function Computation with Private Remote Sources.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

17. M.-C. Chang and M. R. Bloch, “Covert Authentication Against a Myopic Adversary,” in Proc. of IEEE International Symposium on Information Theory, Jul. 2021, pp. 196–201.

    We consider the problem of authenticating communication over a Myopic Binary Adversarial Channel (MBAC) while maintaining covertness with respect to the myopic adversary. When the main channel between legitimate parties is degraded with respect to the adversary’s channel, we show the existence of an integrated scheme that simultaneously exploits secret keys to ensure covertness and authentication. The main technical challenge we address is showing that authentication may be ensured against myopic attacks when using the low-weight codewords mandated by covert communication.

    @inproceedings{Chang2021, author = {Chang, Meng-Che and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Covert Authentication Against a Myopic Adversary}, year = {2021}, month = jul, pages = {196-201}, doi = {10.1109/ISIT45174.2021.9518165}, file = {:2021-Chang-ISIT-Covert Authentication Against a Myopic Adversary.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

18. M.-C. Chang and M. R. Bloch, “Evasive Active Hypothesis Testing,” IEEE Journal on Selected Areas in Information Theory, vol. 2, no. 2, pp. 735–746, Jun. 2021.

    We consider a situation in which a decision maker takes sequential and adaptive sensing actions to collect measurements and estimate an unknown parameter taking finitely many values, in the presence of an adversary who also collects measurements whenever a sensing action is taken. This situation can be viewed as an abstraction in which to analyze the mitigation of information leakage inherent to control actions in systems with feedback, such as cyber-physical systems. Specifically, we formulate an evasive active hypothesis problem in which the objective is for the decision maker to control the risk of its test while minimizing the detection ability of the adversary, measured in terms of the asymptotic error exponent ratio between the adversary and the decision maker. We develop bounds on the exponent ratio that offer insight into optimal strategies that the decision maker can deploy to evade the adversary’s detection. We illustrate the results with a numerical example corresponding to the detection of a wireless transmission.

    @article{Chang2020a, author = {Chang, Meng-Che and Bloch, Matthieu R.}, journal = {IEEE Journal on Selected Areas in Information Theory}, title = {Evasive Active Hypothesis Testing}, year = {2021}, month = jun, number = {2}, pages = {735-746}, volume = {2}, doi = {10.1109/JSAIT.2021.3074156}, file = {:2021-Chang-IEEEJSAIT-Evasive Active Hypothesis Testing.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Journal of Selected Areas in Information Theory}} }

19. M. Bloch et al., “An Overview of Information-Theoretic Security and Privacy: Metrics, Limits and Applications,” IEEE Journal on Selected Areas in Information Theory, vol. 2, no. 1, pp. 5–22, Mar. 2021.

    @article{Bloch2021, author = {Bloch, Matthieu and Gunlu, Onur and Yener, Aylin and Oggier, Frederique and Poor, H. Vincent and Sankar, Lalitha and Schaefer, Rafael F.}, journal = {{IEEE} Journal on Selected Areas in Information Theory}, title = {An Overview of Information-Theoretic Security and Privacy: Metrics, Limits and Applications}, year = {2021}, month = mar, number = {1}, pages = {5--22}, volume = {2}, doi = {10.1109/jsait.2021.3062755}, file = {:2021-Bloch-JSAIT-An Overview of Information-Theoretic Security and Privacy Metrics, Limits and Applications.pdf:PDF}, groups = {NSF1955401}, publisher = {Institute of Electrical and Electronics Engineers ({IEEE})} }

20. H. Zivari-Fard, M. Bloch, and A. Nosratinia, “Two-Multicast Channel with Confidential Messages,” IEEE Transactions on Information Forensics and Security, vol. 16, pp. 2743–2758, 2021.

    Motivated in part by the problem of secure multicast distributed storage, we analyze secrecy rates for a channel in which two transmitters simultaneously multicast to two receivers in the presence of an eavesdropper. Achievable rates are calculated via extensions of a technique due to Chia and El Gamal and the method of output statistics of random binning. Outer bounds are derived for both the degraded and non-degraded versions of the channel, and examples are provided in which the inner and outer bounds meet. The inner bounds recover known results for the multiple-access wiretap channel, broadcast channel with confidential messages, and the compound MAC channel. An auxiliary result is also produced that derives an inner bound on the minimal randomness necessary to achieve secrecy in multiple-access wiretap channels.

    @article{Zivari-Fard2018, author = {Zivari-Fard, Hassan and Bloch, Matthieu and Nosratinia, Aria}, journal = {IEEE Transactions on Information Forensics and Security}, title = {Two-Multicast Channel with Confidential Messages}, year = {2021}, issn = {1556-6021}, pages = {2743-2758}, volume = {16}, doi = {10.1109/TIFS.2021.3055031}, eprint = {1902.08657}, file = {:2021-ZivariFard-IEEETransIFS-Two-Multicast Channel With Confidential Messages.pdf:PDF}, groups = {NSF1955401}, howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}}, keywords = {Encoding;Decoding;Receivers;Random variables;Compounds;Interference channels;US Government;Multicasting;compound channel;confidential messages;randomness constraint;stochastic encoder;wire-tap channel} }