Cryptology ePrint Archive: Report 2017/954

Anonymity Trilemma: Strong Anonymity, Low Bandwidth, Low Latency---Choose Two

Debajyoti Das and Sebastian Meiser and Esfandiar Mohammadi and Aniket Kate

Abstract: This work investigates the fundamental constraints of anonymous communication (AC) protocols. We analyze the relationship between bandwidth overhead, latency overhead, and sender anonymity or recipient anonymity against the global passive (network-level) adversary. We confirm the trilemma that an AC protocol can only achieve two out of the following three properties: strong anonymity (i.e., anonymity up to a negligible chance), low bandwidth overhead, and low latency overhead.

We further study anonymity against a stronger global passive adversary that can additionally passively compromise some of the AC protocol nodes. For a given number of compromised nodes, we derive necessary constraints between bandwidth and latency overhead whose violation make it impossible for an AC protocol to achieve strong anonymity. We analyze prominent AC protocols from the literature and depict to which extend those satisfy our necessary constraints. Our fundamental necessary constraints offer a guideline not only for improving existing AC systems but also for designing novel AC protocols with non-traditional bandwidth and latency overhead choices.

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Date: received 27 Sep 2017, last revised 10 Oct 2017

Contact author: das48 at purdue edu

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Version: 20171010:135933 (All versions of this report)

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