International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Password Mistyping in Two-Factor-Authenticated Key Exchange

Vladimir Kolesnikov
Charles Rackoff
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Abstract: Abstract: We study the problem of Key Exchange (KE), where authentication is two-factor and based on both electronically stored long keys and human-supplied credentials (passwords or biometrics). The latter credential has low entropy and may be adversarily mistyped. Our main contribution is the first formal treatment of mistyping in this setting. Ensuring security in presence of mistyping is subtle. We show mistyping-related limitations of previous KE definitions and constructions. We concentrate on the practical two-factor authenticated KE setting where servers exchange keys with clients, who use short passwords (memorized) and long cryptographic keys (stored on a card). Our work is thus a natural generalization of Halevi-Krawczyk and Kolesnikov-Rackoff. We discuss the challenges that arise due to mistyping. We propose the first KE definitions in this setting, and formally discuss their guarantees. We present efficient KE protocols and prove their security.
  title={Password Mistyping in Two-Factor-Authenticated Key Exchange},
  booktitle={IACR Eprint archive},
  keywords={foundations / Key exchange, definition, combined keys, password, biometric},
  note={ICALP 2008 14160 received 28 Sep 2008, last revised 8 Oct 2008},
  author={Vladimir Kolesnikov and Charles Rackoff},