Does Secure Password-Based Authenticated Key Exchange against Leakage of Internal States Exist?

Abstract

In this paper, we raise a question about existence of secure password-based authenticated key exchange against leakage of internal states (i.e., the passwords and session-specific private information). Toward this question, first, we classify six models of adversary's capabilities about leakage. Next, as a result of considerations for 2-party PAKE, we find two negative answers, but also find a positive answer. More specifically, we show that there exists no scheme which is secure in strong leakage models, but we also show that there exists a scheme which is secure in weak leakage models. Also, we consider the case of 3-party setting which is a special setting of password-based authenticated key exchange, and we find similar impossibilities as 2-party setting.