1. Optimal Channel Security Against Fine-Grained State Compromise: The Safety of Messaging 2018 Crypto SecureChannels
    Joseph Jaeger and Igors Stepanovs
    [View PDF on eprint.iacr.org]
    [Show BibTex Citation]

    @misc{cryptoeprint:2018:553,
    author = {Joseph Jaeger and Igors Stepanovs},
    title = {Optimal Channel Security Against Fine-Grained State Compromise: The Safety of Messaging},
    howpublished = {Cryptology ePrint Archive, Report 2018/553},
    year = {2018},
    note = {\url{https://eprint.iacr.org/2018/553}},
    }

We aim to understand the best possible security of a (bidirectional) cryptographic channel against an adversary that may arbitrarily and repeatedly learn the secret state of either communicating party. We give a formal security definition and a proven-secure construction. This construction provides better security against state compromise than the Signal Double Ratchet Algorithm or any other known channel construction. To facilitate this we define and construct new forms of public-key encryption and digital signatures that update their keys over time.

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