Cryptanalysis of a provably secure cross-realm client-to-client password-authenticated key agreement protocol of CANS '09

Abstract

In this paper, we cryptanalyze the recent smart card based client-to-client password-authenticated key agreement (C2C-PAKA-SC) protocol for cross-realm settings proposed at CANS '09. While client-to-client password-authenticated key exchange (C2C-PAKE) protocols exist in literature, what is interesting about this one is that it is the only such protocol claimed to offer security against password compromise impersonation without depending on public-key cryptography, and is one of the few C2C-PAKE protocols with provable security that has not been cryptanalyzed. We present three impersonation attacks on this protocol; the first two are easier to mount than the designer-considered password compromise impersonation. Our results are the first known cryptanalysis results on C2C-PAKA-SC. © 2011 Springer-Verlag.