Cryptology ePrint Archive: Report 2018/553

Optimal Channel Security Against Fine-Grained State Compromise: The Safety of Messaging

Joseph Jaeger and Igors Stepanovs

Abstract: 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.

Category / Keywords: Secure channel, forward/backward security, security models

Original Publication (with major differences): IACR-CRYPTO-2018

Date: received 3 Jun 2018, last revised 20 Aug 2018

Contact author: istepano at eng ucsd edu

Available format(s): PDF | BibTeX Citation

Note: The proceedings version of this paper contained a security flaw. This is the full, fixed version.

Version: 20180820:161159 (All versions of this report)

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