On the role of feedback in two-way secure communication

He Xiang, Yener Aylin

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    18 Scopus citations


    For bi-directional communication, the most general form of encoders should consider the signals received in the past as inputs. However, in practice, it would also be highly desirable if feedback could be ignored for encoding purposes since this would lead to a simple system design. In this work, we investigate the question of whether and how much loss in secrecy rate would be incurred, if such an approach were taken. To do so, we investigate the role of feedback in secrecy for two three-node two-way channel models. First, we show that feedback is indeed useful for a class of full-duplex two-way wire-tap channels. In this case, when feedback is ignored, the channel is equivalent to a Gaussian degraded relay channel with confidential messages to the relay. The usefulness of feedback is demonstrated by deriving an upper bound for this channel when feedback is ignored, and then proving that, when feedback is used, a secrecy rate higher than this upper bound is achievable. Secondly, we consider the half-duplex Gaussian two-way relay channel where there is an eavesdropper co-located with the relay node, and find that the impact of feedback is less pronounced compared to the previous scenario. Specifically, the loss in secrecy rate, when ignoring the feedback, is quantified to be less than 0.5 bit per channel use when the power of the relay goes to infinity. We also show that this rate region is achievable under a simple time sharing scheme with cooperative jamming, which, with its simplicity and nearoptimum performance, is a viable alternative to an encoder using feedback.

    Original languageEnglish (US)
    Title of host publication2008 42nd Asilomar Conference on Signals, Systems and Computers, ASILOMAR 2008
    Number of pages5
    StatePublished - 2008
    Event2008 42nd Asilomar Conference on Signals, Systems and Computers, ASILOMAR 2008 - Pacific Grove, CA, United States
    Duration: Oct 26 2008Oct 29 2008

    Publication series

    NameConference Record - Asilomar Conference on Signals, Systems and Computers
    ISSN (Print)1058-6393


    Other2008 42nd Asilomar Conference on Signals, Systems and Computers, ASILOMAR 2008
    Country/TerritoryUnited States
    CityPacific Grove, CA

    All Science Journal Classification (ASJC) codes

    • Signal Processing
    • Computer Networks and Communications


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