Advances in Cryptology – EUROCRYPT 2005

Volume 3494 of the series Lecture Notes in Computer Science pp 404-421

Universally Composable Password-Based Key Exchange

  • Ran CanettiAffiliated withIBM T.J. Watson Research Center
  • , Shai HaleviAffiliated withIBM T.J. Watson Research Center
  • , Jonathan KatzAffiliated withDept. of Computer Science, University of Maryland
  • , Yehuda LindellAffiliated withDepartment of Computer Science, Bar-Ilan University
  • , Phil MacKenzieAffiliated withBell Labs, Lucent Technologies


We propose and realize a definition of security for password-based key exchange within the framework of universally composable (UC) security, thus providing security guarantees under arbitrary composition with other protocols. In addition, our definition captures some aspects of the problem that were not adequately addressed by most prior notions. For instance, it does not assume any underlying probability distribution on passwords, nor does it assume independence between passwords chosen by different parties. We also formulate a definition of password-based secure channels, and show that such a definition is achievable given password-based key exchange.

Our protocol realizing the new definition of password-based key exchange is in the common reference string model and relies on standard number-theoretic assumptions. The components of our protocol can be instantiated to give a relatively efficient solution which is conceivably usable in practice. We also show that it is impossible to satisfy our definition in the “plain” model (e.g., without a common reference string).