ID-based authenticated group key agreement from bilinear maps

Abstract

Authenticated group key agreement (GKA) is an important cryptographic mechanism underlying many collaborative and distributed applications. Recently, identity (ID)-based authenticated GKA has been increasingly researched because of the authentication and simplicity of the ID-based cryptosystem. However, there are two disadvantages with this kind of mechanism: 1) the private key escrow is inherent and 2) the Private Key Generator (PKG) must send client private keys over secure channels, making private key’s distribution difficult. The two disadvantages, particularly secure channels, may be unacceptable for secure group communications application. Fortunately, we can avoid both of them. In this paper, with bilinear maps on ECC, we present a new authenticated group key agreement protocol that does not require secure channels. The basic idea is the usual way of circumventing escrow: double key and double encryption (verification). The secret key of a user is generated by a key generation center (KGC) and the user collaboratively. Each of them has “half” of the secret information about the secret key of the user, and there is no secret key distribution problem. In addition, the computation cost of the protocol is very low because the main computation is binary addition.