Deniable version of SIGMA key exchange protocol resilient to ephemeral key leakage

Abstract

We propose modifications of SIGMA key exchange protocol that provide the deniability property. Our proposition, based on ring signatures, provide the possibility that a single party alone can produce a simulated transcripts of the protocol without the peer participation. Moreover we strengthen the SIGMA resulting session keys by additional using of long-term keys in the Diffie-Hellman key exchange phase of the protocol. Our proposition preserves the modular construction of the protocol, and does not change the number of the protocol rounds.