Threshold password-authenticated key retrieval protocol using bilinear pairings

Abstract

These days many real world systems still rely on password authentication to verify the user``s identity before allowing that user to be given certain network services. So far many protocols based on password have been proposed, even if there are many security concerns associated with password-based protocol. Thus many researchers have studied how to make the password-like weak key to be more stronger one. On the other hand, with rapid development on the Internet, users can easily access the network anywhere and anytime, which is so called ubiquitous computing paradigm. Thus, we want to give users password-authenticated access to private keys from anywhere, while protecting the password and those private keys from being revealed to an attacker. We present a new threshold password-authenticated key retrieval protocol that allows a $\emph{roaming user}$, who accesses a network from different client terminals, to download a private key from remote servers with knowledge of only his identity and password information, assuming that the user does not carry the smart card storing user``s private information. We note that as a goal of a multi-server roaming system, the 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 $\emph{threshold password-only roaming protocol using bilinear pairings}$. In this paper, we use $\emph{(k,n)-threshold scheme}$ in which only $\emph{k}$ 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.