Paper 2008/527

Properties of Cryptographic Hash Functions

Michal Rjaško

Abstract

This paper extends the work of Rogaway and Shrimpton (2004), where they formalized seven security properties: notions of preimage resistance (Pre, aPre, ePre), second-preimage resistance (Sec, aSec, eSec) and collision resistance (Coll). They also give all the implications and separations among the properties. In this paper we consider three additional security properties which are important in applications of hash functions: unforgeability (MAC), pseudo-random function (Prf) and pseudo-random oracle (Pro). We give a new type of the implication and separation between the security notions since the ones defined by Rogaway and Shrimpton were too constraining, and work out all the relationships among the ten security notions above. Some of the relations have been proven before, some of them appear to be new. We show that a property pseudo-random oracle (Pro) introduced by Coron, Dodis, Malinaud and Puniya is (as expected) the strongest one, since it implies almost all of the other properties.