Efficient Solution to Password-based Key Exchange for Large Groups

This paper presents an efficient solution to key exchange problem for large groups in the password-based scenario. Our scheme can combine existing group protocols to get a hybrid group key exchange protocol which is efficient in terms of both computation and communication. And the resulting protocol allows users to securely join and leave the group at any time—the so-called dynamic case. For dynamic group communications, we propose an efficient keyupdating algorithms so that the group key is only known to the members of the newly formed pool. Furthermore, our proposal does not introduce new idealizing assumptions or high entropy secrets for authentication.