Paper 2008/214

Multi-Factor Password-Authenticated Key Exchange

Douglas Stebila, Poornaprajna Udupi, and Sheueling Chang


We consider a new form of authenticated key exchange which we call multi-factor password-authenticated key exchange, where session establishment depends on successful authentication of multiple short secrets that are complementary in nature, such as a long-term password and a one-time response, allowing the client and server to be mutually assured of each other's identity without directly disclosing private information to the other party. Multi-factor authentication can provide an enhanced level of assurance in higher security scenarios such as online banking, virtual private network access, and physical access because a multi-factor protocol is designed to remain secure even if all but one of the factors has been compromised. We introduce the first formal security model for multi-factor password-authenticated key exchange protocols, propose an efficient and secure protocol called MFPAK, and provide a formal argument to show that our protocol is secure in this model. Our security model is an extension of the Bellare-Pointcheval-Rogaway security model for password-authenticated key exchange and the formal analysis proceeds in the random oracle model.

Note: Full version.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Australian Information Security Conference (AISC) 2010. CRPIT volume 105, pages 56--66. Australian Computer Society.
Contact author(s)
douglas @ stebila ca
2010-08-25: revised
2008-05-23: received
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Creative Commons Attribution


      author = {Douglas Stebila and Poornaprajna Udupi and Sheueling Chang},
      title = {Multi-Factor Password-Authenticated Key Exchange},
      howpublished = {Cryptology ePrint Archive, Paper 2008/214},
      year = {2008},
      note = {\url{}},
      url = {}
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