Credential Authenticated Identification and Key Exchange

Abstract

This paper initiates a study of two-party identification and key-exchange protocols in which users authenticate themselves by proving possession of credentials satisfying arbitrary policies, instead of using the more traditional mechanism of a public-key infrastructure. Definitions in the universal composability framework are given, and practical protocols satisfying these definitions, for policies of practical interest, are presented. All protocols are analyzed in the common reference string model, assuming adaptive corruptions with erasures, and no random oracles. The new security notion includes password-authenticated key exchange as a special case, and new, practical protocols for this problem are presented as well, including the first such protocol that provides resilience against server compromise (without random oracles).