Hash functions in the dedicated-key setting: Design choices and MPP transforms

Abstract

In the dedicated-key setting, one uses a compression function f: {0, 1}k × {0, 1}n+d → {0, 1}n to build a family of hash functions Hf: Κ × M → {0, 1} n indexed by a key space Κ. This is different from the more traditional design approach used to build hash functions such as MD5 or SHA-1, in which compression functions and hash functions do not have dedicated key inputs. We explore the benefits and drawbacks of building hash functions in the dedicated-key setting (as compared to the more traditional approach), highlighting several unique features of the former. Should one choose to build hash functions in the dedicated-key setting, we suggest utilizing multi-property-preserving (MPP) domain extension transforms. We analyze seven existing dedicated-key transforms with regard to the MPP goal and propose two simple new MPP transforms. © Springer-Verlag Berlin Heidelberg 2007.