A formal framework for verifying IKA property of protocols

Abstract

A group key agreement (GKA) protocol generates a secret key (session key) shared among the members of the group, from the contributions made by group members. GKA protocols are expected to satisfy the property of Implicit Key Authentication (IKA) which assures group members that the key generated by the protocol is not accessible to any member outside the group. In this article, we propose a technique to prove the correctness of GKA protocols with respect to IKA. We establish the soundness of our proposal and also illustrate its application.Normally IKA property of protocols is established by proving that the protocol satisfies authentication of participants and secrecy of the session keys. Most formal models would be able to analyze a GKA protocol with respect to IKA, using the above approach. However analysis of two security properties, namely authentication and secrecy, would increase the chances of errors. We propose a single condition for verifying whether the GKA protocol satisfies IKA. Keywords: Group Key Agreement Protocols, Implicit Key Authentication, Strand Spaces, Formal Framework