Chapter

Fast Software Encryption

Volume 6147 of the series Lecture Notes in Computer Science pp 192-211

Enhanced Security Notions for Dedicated-Key Hash Functions: Definitions and Relationships

  • Mohammad Reza ReyhanitabarAffiliated withCentre for Computer and Information Security Research, School of Computer Science and Software Engineering, University of Wollongong
  • , Willy SusiloAffiliated withCentre for Computer and Information Security Research, School of Computer Science and Software Engineering, University of Wollongong
  • , Yi MuAffiliated withCentre for Computer and Information Security Research, School of Computer Science and Software Engineering, University of Wollongong

Abstract

In this paper, we revisit security notions for dedicated-key hash functions, considering two essential theoretical aspects; namely, formal definitions for security notions, and the relationships among them. Our contribution is twofold. First, we provide a new set of enhanced security notions for dedicated-key hash functions. The provision of this set of enhanced properties has been motivated by the introduction of the enhanced target collision resistance (eTCR) property by Halevi and Krawczyk at Crypto 2006. We notice that the eTCR property does not belong to the set of the seven security notions previously investigated by Rogaway and Shrimpton at FSE 2004; namely: Coll, Sec, aSec, eSec, Pre, aPre and ePre. The fact that eTCR, as a new useful property, is the enhanced variant of the well-known TCR (a.k.a. eSec or UOWHF) property motivates one to investigate the possibility of providing enhanced variants for the other properties. We provide such an enhanced set of properties. Interestingly, there are six enhanced variants of security notions available, excluding “ePre” which can be demonstrated to be non-enhanceable. As the second and main part of our contribution, we provide a full picture of the relationships (i.e. implications and separations) among the (thirteen) security properties including the (six) enhanced properties and the previously considered seven properties. The implications and separations are supported by formal proofs (reductions) and/or counterexamples in the concrete-security framework.

Keywords

hash functions security notions definitions relationships