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Conference Papers Year : 2022

MARSHAL: Messaging with Asynchronous Ratchets and Signatures for faster HeALing

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Abstract

Secure messaging applications are deployed on devices that can be compromised, lost, stolen, or corrupted in many ways. Thus, recovering from attacks to get back to a clean state is essential and known as healing. Signal is a widely-known, privacy-friendly messaging application, that uses key-ratcheting mechanism updates keys at each stage to provide end-to-end channel security, forward secrecy, and post-compromise security. We strengthen this last property, by providing a faster healing. Signal needs up to two full chains of messages before recovering, our protocol enables recovery after the equivalent of a chain of only one message. We also provide an extra protection against session-hijacking attacks. We do so, while building on the pre-existing Signal backbone, without weakening its other security assumptions, and still being compatible with Signal's out-of-order message handling feature. Our implementation results show that, while slower than Signal (as expected), MARSHAL's spectacular gain in healing speed comes at a surprisingly low cost, with individual stages (including keyderivation, encryption, and decryption) taking less than 6 ms.
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Dates and versions

hal-03510612 , version 1 (04-01-2022)

Identifiers

Cite

Olivier Blazy, Pierre-Alain Fouque, Thibaut Jacques, Pascal Lafourcade, Cristina Onete, et al.. MARSHAL: Messaging with Asynchronous Ratchets and Signatures for faster HeALing. The 37th ACM/SIGAPP Symposium on Applied Computing, SAC (2022), Apr 2022, Virtual, Czech Republic. pp.1-8, ⟨10.1145/3477314.3507044⟩. ⟨hal-03510612⟩
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