# Information Bytes

Matthieu Bloch
School of Electrical and Computer Engineering
Georgia Institute of Technology

# Recent works

1. M. Tahmasbi and M. R. Bloch, “Covert Secret Key Generation with an Active Warden,” IEEE Transactions on Information Forensics and Security, vol. 15, pp. 1026–1039, Jun. 2020.

We investigate the problem of covert and secret key generation over a state-dependent discrete memoryless channel with one-way public discussion in which an adversary, the warden, may arbitrarily choose the channel state. We develop an adaptive protocol that, under conditions that we explicitly specify, not only allows the transmitter and the legitimate receiver to exchange a secret key but also conceals from the active warden whether the protocol is being run. When specialized to passive adversaries that do not control the channel state, we partially characterize the covert secret key capacity. In particular, the covert secret key capacity is sometimes equal to the covert capacity of the channel, so that secrecy comes “for free.”

@article{Tahmasbi2019,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R},
title = {Covert Secret Key Generation with an Active Warden},
journal = {IEEE Transactions on Information Forensics and Security},
year = {2020},
volume = {15},
pages = {1026-1039},
month = jun,
doi = {10.1109/TIFS.2019.2932906},
eprint = {1901.02044},
file = {:2020-Tahmasbi-IEEETransIFS.pdf:PDF},
groups = {Steganography and covert communications},
howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}}
}


2. M. Tahmasbi, M. R. Bloch, and A. Yener, “Learning an Adversary’s Actions for Secret Communication,” IEEE Transactions on Information Theory, vol. 3, no. 66, pp. 1607–1624, Mar. 2020.

@article{Tahmasbi2018,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R. and Yener, Aylin},
journal = {IEEE Transactions on Information Theory},
title = {Learning an Adversary's Actions for Secret Communication},
year = {2020},
month = mar,
number = {66},
pages = {1607--1624},
volume = {3},
doi = {10.1109/TIT.2019.2940960},
eprint = {1807.08670},
file = {:2020-Tahmasbi-IEEETransIT-a.pdf:PDF},
howpublished = {accepted to \emph{IEEE Transactions on Information Theory}}
}


3. M. Tahmasbi and M. R. Bloch, “Steganography Protocols for Quantum Channels.” submitted to Journal of Mathematical Physics, Feb. 2020.

@misc{Tahmasbi2020a,
author = {Tahmasbi, Mehrdad and Bloch, Matthieu R},
howpublished = {submitted to \emph{Journal of Mathematical Physics}},
month = feb,
title = {Steganography Protocols for Quantum Channels},
year = {2020}
}


4. G. Cervia, L. Luzzi, M. Le Treust, and M. Bloch, “Strong Coordination of Signals and Actions over Noisy Channels with two-sided State Information.” accepted to IEEE Transactions on Information Theory, Feb. 2020.

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},
howpublished = {accepted to \emph{IEEE Transactions on Information Theory}},
month = feb,
title = {Strong Coordination of Signals and Actions over Noisy Channels with two-sided State Information},
year = {2020},
eprint = {1801.10543}
}