Anonymous and Transparent Gateway-based Password-Authenticated Key Exchange

Michel Abdalla (1, 2) , Malika Izabachène (1, 2) , David Pointcheval (1, 2)

1 LIENS - Laboratoire d'informatique de l'école normale supérieure
2 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities

In Asiacrypt 2005, Abdalla et al. put forward the notion of gateway-based password- authenticated key exchange (GPAKE) protocol, which allows clients and gateways to establish a common session key with the help of an authentication server. In addition to the semantic security of the session key, their solution also provided additional security properties such as password pro- tection with respect to malicious gateways and key privacy with respect to curious authentication servers. In this paper, we further pursue this line of research and present a new and stronger se- curity model for GPAKE schemes, combining all above-mentioned security properties. In addition to allowing a security proof for all these security properties, the new security model has also other advantages over the previous one such as taking into account user corruptions. After describing the new security model, we then present a new variant of the GPAKE scheme of Abdalla et al. with similar efficiency. Like the original scheme, the new scheme is also transparent in that it does not differ significantly from a classical 2-PAKE scheme from the point of view of a client. Finally, we also show how to add client anonymity with respect to the server to the basic GPAKE scheme by using private information retrieval protocols.

Domaines: Cryptographie et sécurité [cs.CR]

Michel Abdalla, Malika Izabachène, David Pointcheval. Anonymous and Transparent Gateway-based Password-Authenticated Key Exchange. The 7th International Workshop on Cryptology and Network Security (CANS '08), 2008, Hong-Kong, China. pp.133--148. ⟨inria-00419150⟩