Password-based Encrypted Group Key Agreement

This paper presents an efficient password-based authenticated encrypted group key agreement protocol immune to dictionary attack under the computation Diffie-Hellman (CDH) assumption. In a password-based key agreement protocol, the users only share a human-memorable low entropy password; and using this low-entropy password, the users can agree upon a high-entropy session key which they may use to build a secure communication channel among themselves. While designing such protocols, one should limit the number of on-line password guessing and achieve the security against dictionary attack. Our protocol is obtained from the multi-party key agreement protocol of Kim et al. We analyze the security in the security model formalized by Bellare et al. following their proof techniques. Our proposed scheme achieves efficiency in both communication and computation aspects and is proven to be secure in both the ideal cipher model and the random oracle model.