文摘
With the assistance of an authentication server, a gateway-oriented password-authenticated key exchange (GPAKE) protocol can establish a common session key shared between a client and a gateway. Unfortunately, a GPAKE protocol becomes totally insecure if an adversary can compromise the authentication server and steal the passwords of the clients. In order to provide resilience against adversaries who can hack into the authentication server, we propose a threshold GPAKE protocol and then present its security proof in the standard model based on the hardness of the decisional Diffie-Hellman (DDH) problem. In our proposal, the password is shared among n authentication servers and is secure unless the adversary corrupts more than t+1 servers. Our protocol requires n > 3t servers to work. Compared with existing threshold PAKE protocols, our protocol maintains both stronger security and greater efficiency.