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
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 (of Boyen et al. [6,7,10] and Kolesnikov and Rackoff ).
We concentrate on the practical two-factor authenticated KE setting where
exchange keys with
, 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.