We present a new threshold password-based authentication protocol that allows a roaming user(a user who accesses a network from different client terminals) to download a private key from remote servers with knowledge of only his identity and password. He does not carry the smart card storing user's private information. We note that as a goal of a multi-server roaming system, a protocol has to allow a user to get his private key from the servers, even if some of the servers are compromised. With this point of view, we give the first description of a threshold password-only roaming protocol. In this paper, we use (k,n)-threshold scheme in which only k honest servers or more are engaged to reconstruct a secret key. Our scheme is based on bilinear pairings which could be built from Weil pairing or Tate pairing.

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