Privacy-oriented dependency via deniable SIGMA protocol

The IoT era has led to a complex interplay between the communication security and the storage service providers. The secure key exchange is crucial from the perspective of communication confidentiality. Similarly, the evidence-based cryptography provides the crucial feature such as accountability with respect to both, the participating entities as well as the protocol instance. However, privacy concerned applications and user perspective regarding protocol instance execution require exactly opposite features, i.e., deniability. There is no denying about the relevance of this feature in the application that might incur a heavy payoff to a user, in case application went malicious. Therefore, the deniability feature provides a protection shield beyond the application execution as well as user participation. We propose a key exchange protocol that is based on SIGMA key exchange protocol and still provides assurance on deniability feature. In particular, this stronger notion of deniability (as featured in our protocol) is defined through a distinguisher algorithm provided with an entire set of public keys, secret keys, and the ephemeral Diffie–Hellman key of the denying party. Our proposition, based on ring signatures, provide the justification of the fact that any single party alone can produce simulated transcripts of the protocol (without any peer participation), thereby, supporting the deniability feature. Moreover, we strengthen the SIGMA resulting session keys by involving (in addition) long-term keys during the Diffie–Hellman key exchange phase of the protocol. Our proposition preserves the modular construction of the protocol and does not require an increased number of the protocol rounds as a compensation for added deniability features.