Deniability for protocols with shared state with applications to Anonymous Authentication

Author: Alonso González, and A.H..


In this work we propose a different approach to solve the problem of anonymous authentication (Boneh et al. CCS 1999). Instead of the classical solution that uses ring signatures, we directly combine an an anonymous channel with deniable authentication without contradicting anonymity. The classical solution provides anonymity with respect to a set of authorized users, our solution provides anonymity with respect to authorized and no authorized (but maybe authorized for other group) users at the price of a different form of anonimity. We develop new tools to prove deniability of protocols in the Generalized Universal Composability framework (GUC, Canetti et al. TCC 2007). In particular we define deniability for multi party protocols, and show that deniable protocols are exactly those protocols that realize the ideal functionality F den . This result enable us to prove deniability of many UC and GUC functionalities. We use our new tools to design a functionality for Anonymous Authenticated Channels and design a protocol that realizes it in the GUC framework.

Ref: DCC Technical Report, June 2014 (PDF) & eprint Archive (PDF).