International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 24 May 2024

Joseph Jaeger, Akshaya Kumar, Igors Stepanovs
ePrint Report ePrint Report
We introduce a new cryptographic primitive called symmetric signcryption, which differs from traditional signcryption because the sender and recipient share a secret key. We prove that a natural composition of symmetric encryption and signatures achieves strong notions of security against attackers that can learn and control many keys. We then identify that the core encryption algorithm of the Keybase encrypted messaging protocol can be modeled as a symmetric signcryption scheme. We prove the security of this algorithm, though our proof requires assuming non-standard, brittle security properties of the underlying primitives.
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