nPAKE: An Improved Group PAKE Protocol

In this paper, we propose an improved password-based authentication key exchange protocol for group, which called nPAKE. In the protocol, each client shares a password with the server and the adjacent clients share a temporary encryption key with the help of server, so it can reduce the communication costs between the clients and server. nPAKE protocol is based on the chosen-based computation Diffie-Hellman assumption. By security analysis, we show that our protocol can resist the dictionary attacks, Tang-Chen attack and man-in-the-middle attack.