Light-weight key exchange with different passwords in the standard model

In this paper, we consider password-based authenticated key exchange with different passwords, where the users only share a password with the trusted server but do not share between themselves. The server helps the users share a cryptographi-cally secure session key by using their different passwords. We propose a light-weight password-based authenticated key exchange protocol with different passwords, i.e., it requires only 2 rounds and 4 modular exponentiations per user. The protocol provides forward secrecy, known-key secrecy, key secrecy against the curious server, and security against undetectable online dictionary attacks without random oracles.