Theoretical and Algorithmic Foundations of Covert Quantum-Secured Networks

Award information

Abstract

With the widespread of communication networks, protecting the ever growing amount of sensitive information transiting through these channels has become a daunting challenge; in an ever more complex and competitive interconnected world, the mere act of creating and communicating sensitive information may become a liability. This project will help address this security challenge by developing systems that exploit quantum properties (such as those of photons encountered in optical systems) to ensure that communications can remain secret (in the sense that the information content is protected) and covert (in the sense that the presence of communication cannot be detected). The project will develop theoretical models in quantum information theory and algorithms that offer provable guarantees for secrecy and covertness. In addition to investigating quantum information-theoretic aspects of secure covert communications, the research team will mentor students engaged in this research, develop a graduate level course on quantum information theory, and engage in collaborative efforts to experimentally test and demonstrate the proposed models and algorithms.

The project will design and analyze protocols for communication over quantum channels between legitimate parties, in such a way that the parties can provably assert if their communication has been detected and generate secret keys with provably low-probability of detection. Supported by preliminary results, this project will explore how to encode information onto sequences of quantum states and how to decode the sequences after transmission through a noisy channel, in such a way that adversaries that are limited only by the laws of quantum physics can neither detect nor extract information. The main challenge addressed is how to reconcile the need for using an extremely diffuse information content to escape detection while still being able to process the information at a receiver. The performance of the proposed secret and covert key generation protocols will be compared to that of established quantum key distributions protocols through the development of a precise quantum information-theoretic framework in which to study the possibility of covert and secret key generation over quantum channels; the design of low-complexity algorithms allowing one to process the diffuse statistical information content of covert signals; and the experimental validation of theoretical models and algorithm in an optical testbed.

Publications

1. S.-Y. Wang, S.-J. Su, and M. R. Bloch, “Resource-Efficient Entanglement-Assisted Covert Communications over Bosonic Channels,” in Proc. of IEEE International Symposium on Information Theory, Athens, Greece, Jul. 2024, pp. 3106–3111.

   @inproceedings{Wang2024Resource, author = {Wang, Shi-Yuan and Su, Shang-Jen and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Resource-Efficient Entanglement-Assisted Covert Communications over Bosonic Channels}, year = {2024}, address = {Athens, Greece}, month = jul, pages = {3106-3111}, doi = {10.1109/ISIT57864.2024.10619663}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

2. S.-Y. Wang, M.-C. Chang, and M. R. Bloch, “Covert Joint Communication and Sensing Under Variational Distance Constraint,” in Proc. of 58th Annual Conference on Information Sciences and Systems, Princeton, JN, Mar. 2024.

   @inproceedings{Wang2024Covert, author = {Wang, Shi-Yuan and Chang, Meng-Che and Bloch, Matthieu R.}, booktitle = {Proc. of 58th Annual Conference on Information Sciences and Systems}, title = {Covert Joint Communication and Sensing Under Variational Distance Constraint}, year = {2024}, address = {Princeton, JN}, month = mar, doi = {10.1109/CISS59072.2024.10480161}, file = {:2024-Wang-CISS-Covert Joint Communication and Sensing under Variational Distance Constraint.pdf:PDF}, groups = {NSF1910859, NSF2148400}, howpublished = {accepted to \emph{58th Annual Conference on Information Sciences and Systems}} }

3. 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}} }

4. S.-Y. Wang, T. Erdoğan, U. Pereg, and M. R. Bloch, “Joint Quantum Communication and Sensing,” in Proc. of IEEE Information Theory Workshop, Aug. 2022, pp. 506–511.

   @inproceedings{Wang2022Joint, author = {Wang, Shi-Yuan and Erdo\u{g}an, Tuna and Pereg, Uzi and Bloch, Matthieu R}, booktitle = {Proc. of IEEE Information Theory Workshop}, title = {Joint Quantum Communication and Sensing}, year = {2022}, month = aug, pages = {506-511}, doi = {10.1109/ITW54588.2022.9965810}, file = {:2022-Wang-ITW-Joint Quantum Communication and Sensing.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Information Theory Workshop}} }

5. S.-Y. Wang, T. Erdoğan, and M. R. Bloch, “Towards a Characterization of the Covert Capacity of Bosonic Channels under Trace Distance,” in Proc. of IEEE International Symposium on Information Theory, Helsinki, Finland, Jun. 2022, pp. 354–359.

   @inproceedings{Wang2022Towards, author = {Wang, Shi-Yuan and Erdo\u{g}an, Tuna and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Towards a Characterization of the Covert Capacity of Bosonic Channels under Trace Distance}, year = {2022}, address = {Helsinki, Finland}, month = jun, pages = {354--359}, doi = {10.1109/ISIT50566.2022.9834394}, file = {:2022-Wang-ISIT-Towards a Characterization of the Covert Capacity of Bosonic Channels under Trace Distance.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

6. 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}} }

7. U. Pereg, R. Ferrara, and M. R. Bloch, “Key Assistance, Key Agreement, and Layered Secrecy for Bosonic Broadcast Channels,” in Proc. of IEEE Information Theory Workshop, Oct. 2021, pp. 1–6.

   @inproceedings{Pereg2021, author = {Pereg, Uzi and Ferrara, Roberto and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE Information Theory Workshop}, title = {Key Assistance, Key Agreement, and Layered Secrecy for Bosonic Broadcast Channels}, year = {2021}, month = oct, pages = {1-6}, doi = {10.1109/ITW48936.2021.9611359}, file = {:2021-Pereg-ITW-Key Assistance, Key Agreement, and Layered Secrecy for Bosonic Broadcast Channels.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Information Theory Workshop}} }

8. S.-Y. Wang and M. R. Bloch, “Covert MIMO Communications under Variational Distance Constraint,” IEEE Transactions on Information Forensics and Security, vol. 16, pp. 4605–4620, Sep. 2021.

   The problem of covert communication over Multiple-Input Multiple-Output (MIMO) Additive White Gaussian Noise (AWGN) channels is investigated, in which a transmitter attempts to reliably communicate with a legitimate receiver while avoiding detection by a passive adversary. The covert capacity of the MIMO AWGN channel is characterized under a variational distance covertness constraint when the MIMO channel matrices are static and known. The characterization of the covert capacity is also extended to a class of channels in which the legitimate channel matrix is known but the adversary’s channel matrix is only known up to a rank and a spectral norm constraint.

   @article{Wang2021, author = {Wang, Shi-Yuan and Bloch, Matthieu R}, journal = {IEEE Transactions on Information Forensics and Security}, title = {Covert MIMO Communications under Variational Distance Constraint}, year = {2021}, month = sep, pages = {4605 - 4620}, volume = {16}, doi = {10.1109/TIFS.2021.3110048}, eprint = {2102.11336}, file = {:2021-Wang-IEEETransIFS-Covert MIMO Communications under Variational Distance Constraint.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Transactions on Information Forensics and Security}} }

9. S.-Y. Wang and M. R. Bloch, “Explicit Design of Provably Covert Channel Codes,” in Proc. of IEEE International Symposium on Information Theory, Jul. 2021, pp. 190–195.

   @inproceedings{Wang2021a, author = {Wang, Shi-Yuan and Bloch, Matthieu R.}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Explicit Design of Provably Covert Channel Codes}, year = {2021}, month = jul, pages = {190-195}, doi = {10.1109/ISIT45174.2021.9517930}, file = {:2021-Wang-ISIT-Explicit Design of Provably Covert Channel Codes.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

10. M. Tahmasbi, B. Bash, S. Guha, and M. R. Bloch, “Signaling for Covert Quantum Sensing,” in Proc. of IEEE International Symposium on Information Theory, Jul. 2021, pp. 1041–1045.

    @inproceedings{Tahmasbi2021, author = {Tahmasbi, Mehrdad and Bash, Boulat and Guha, Saikat and Bloch, Matthieu R}, booktitle = {Proc. of IEEE International Symposium on Information Theory}, title = {Signaling for Covert Quantum Sensing}, year = {2021}, month = jul, pages = {1041-1045}, doi = {10.1109/ISIT45174.2021.9517722}, file = {:2021-Tahmasbi-ISIT-Signaling for Covert Quantum Sensing.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE International Symposium on Information Theory}} }

11. M. Tahmasbi and M. R. Bloch, “On Covert Quantum Sensing and the Benefits of Entanglement,” IEEE Journal on Selected Areas in Information Theory, vol. 2, no. 1, pp. 352–365, Mar. 2021.

    Motivated by applications to covert quantum radar, we analyze a covert quantum sensing problem, in which a legitimate user aims at estimating an unknown parameter taking finitely many values by probing a quantum channel while remaining undetectable from an adversary receiving the probing signals through another quantum channel. When channels are classical-quantum, we characterize the optimal error exponent under a covertness constraint for sensing strategies in which probing signals do not depend on past observations. When the legitimate user’s channel is a unitary depending on the unknown parameter, we provide achievability and converse results that show how one can significantly improve covertness using an entangled input state.

    @article{Tahmasbi2020c, author = {Tahmasbi, Mehrdad and Bloch, Matthieu R.}, journal = {IEEE Journal on Selected Areas in Information Theory}, title = {On Covert Quantum Sensing and the Benefits of Entanglement}, year = {2021}, issn = {2641-8770}, month = mar, number = {1}, pages = {352-365}, volume = {2}, doi = {10.1109/JSAIT.2021.3056640}, eprint = {2008.01264}, file = {:/Users/mbloch/Downloads/2021-Tahmasbi-JSAIT-On covert quantum sensing and the benefits of entanglement-pdfa.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Journal of Selected Areas in Information Theory}}, keywords = {Sensors;Quantum channel;Testing;Quantum entanglement;Channel estimation;Quantum state;Tensors;Quantum sensing;covert communication} }

12. M. Tahmasbi and M. R. Bloch, “Covert and secret key expansion over quantum channels under collective attacks,” IEEE Transactions on Information Theory, vol. 66, no. 11, pp. 7113–7131, Nov. 2020.

    We consider an enhanced measure of security for a quantum key distribution protocol, in which we require not only that the adversary obtains no information about the key but also remains unaware that a key generation protocol has been executed. When the adversary applies the same quantum channel independently to 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. A crucial component of the protocol is a covert estimation stage, which is then combined with universal channel coding for reliability and resolvability in the covert regime.

    @article{Tahmasbi2019a, author = {Tahmasbi, Mehrdad and Bloch, Matthieu R}, journal = {IEEE Transactions on Information Theory}, title = {Covert and secret key expansion over quantum channels under collective attacks}, year = {2020}, issn = {1557-9654}, month = nov, number = {11}, pages = {7113-7131}, volume = {66}, doi = {10.1109/TIT.2020.3021595}, file = {:2020-Tahmasbi-IEEETransIT-b.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Transactions on Information Theory}} }

13. M. Tahmasbi and M. R. Bloch, “Steganography Protocols for Quantum Channels,” Journal of Mathematical Physics, vol. 61, no. 8, p. 082201, Aug. 2020.

    We study several versions of a quantum steganography problem in which two legitimate parties attempt to conceal a cypher in a quantum cover transmitted over a quantum channel without arising suspicion from a warden who intercepts the cover. In all our models, we assume that the warden has an inaccurate knowledge of the quantum channel and we formulate several variations of the steganography problem depending on the tasks used as the cover and the cypher task. In particular, when the cover task is classical communication, we show that the cypher task can be classical communication or entanglement sharing; when the cover task is entanglement sharing and the main channel is noiseless, we show that the cypher task can be randomness sharing; when the cover task is quantum communication and the main channel is noiseless, we show that the cypher task can be classical communication. In the latter case, our results improve earlier ones by relaxing the need for a shared key between the transmitter and the receiver and hold under milder assumptions on the cover quantum communication code. We study several versions of a quantum steganography problem in which two legitimate parties attempt to conceal a cypher in a quantum cover transmitted over a quantum channel without arising suspicion from a warden who intercepts the cover. In all our models, we assume that the warden has an inaccurate knowledge of the quantum channel and we formulate several variations of the steganography problem depending on the tasks used as the cover and the cypher task. In particular, when the cover task is classical communication, we show that the cypher task can be classical communication or entanglement sharing; when the cover task is entanglement sharing and the main channel is noiseless, we show that the cypher task can be randomness sharing; when the cover task is quantum communication and the main channel is noiseless, we show that the cypher task can be classical communication. In the latter case, our results improve earlier ones by relaxing the need for a shared key between the transmitter and the receiver and hold under milder assumptions on the cover quantum communication code.

    @article{Tahmasbi2020a, author = {Tahmasbi, Mehrdad and Bloch, Matthieu R}, journal = {Journal of Mathematical Physics}, title = {Steganography Protocols for Quantum Channels}, year = {2020}, month = aug, number = {8}, pages = {082201}, volume = {61}, doi = {10.1063/5.0004731}, eprint = {1907.09602}, file = {:2020-Tahmasbi-JMP.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{Journal of Mathematical Physics}} }

14. M. Tahmasbi and M. R. Bloch, “Towards Undetectable Quantum Key Distribution over Bosonic Channels,” IEEE Journal on Selected Areas in Information Theory, vol. 1, no. 2, pp. 585–598, Aug. 2020.

    We propose a protocol based on pulse-position modulation and multi-level coding that allows one to bootstrap traditional quantum key distribution protocols while ensuring covertness, in the sense that no statistical test by the adversary can detect the presence of communication over the quantum channel better than a random guess. When run over a bosonic channel, our protocol can leverage existing discrete-modulated continuous-variable protocols. Since existing techniques to bound Eve’s information do not directly apply, we develop a new bound that results in positive, although very low, throughput for a range of channel parameters. The analysis of the protocol performance shows that covert secret key expansion is possible using a public authenticated classical channel and a quantum channel largely but not fully under the control of an adversary, which we precisely define. We also establish a converse result showing that, under the golden standard of quantum key distribution, by which the adversary completely controls the quantum channel, no covert key generation is possible.We propose a protocol based on pulse-position modulation and multi-level coding that allows one to bootstrap traditional quantum key distribution protocols while ensuring covertness, in the sense that no statistical test by the adversary can detect the presence of communication over the quantum channel better than a random guess. When run over a bosonic channel, our protocol can leverage existing discrete-modulated continuous-variable protocols. Since existing techniques to bound Eve’s information do not directly apply, we develop a new bound that results in positive, although very low, throughput for a range of channel parameters. The analysis of the protocol performance shows that covert secret key expansion is possible using a public authenticated classical channel and a quantum channel largely but not fully under the control of an adversary, which we precisely define. We also establish a converse result showing that, under the golden standard of quantum key distribution, by which the adversary completely controls the quantum channel, no covert key generation is possible.

    @article{Tahmasbi2020, author = {Tahmasbi, Mehrdad and Bloch, Matthieu R.}, journal = {IEEE Journal on Selected Areas in Information Theory}, title = {Towards Undetectable Quantum Key Distribution over Bosonic Channels}, year = {2020}, month = aug, number = {2}, pages = {585-598}, volume = {1}, doi = {10.1109/JSAIT.2020.3017212}, eprint = {1904.12363}, file = {:2020-Tahmasbi-IEEEJSAIT-Towards Undetectable Quantum Key Distribution Over Bosonic Channels.pdf:PDF}, groups = {NSF1910859}, howpublished = {accepted to \emph{IEEE Journal of Selected Topics in Information Theory}} }