Cryptology ePrint Archive: Report 2012/009

On the Indifferentiability of the Integrated-Key Hash Functions

Saif Al-Kuwari

Abstract: Most of today's popular hash functions are keyless such that they accept variable-length messages and return fixed-length fingerprints. However, recent separation results reported on several serious inherent weaknesses in these functions, motivating the design of hash functions in the keyed setting. The challenge in this case, however, is that on one hand, it is economically undesirable to abundant the already adopted (keyless) functions in favour of new (keyed) ones, and on the other hand, the process of converting a keyless function to a keyed one is, evidently, non-trivial. A solution to this dilemma is to adopt the "integrated-key" approach that creates keyed hash functions out of "unmodified" keyless primitives. In this paper, we adopt several integrated-key constructions and prove that they are indifferentiable from random oracle, showing in details how to develop indifferentiability proofs at the integrated-key setting. The presented indifferentiability proof is generic and can be applied on other hash functions constructed in this setting with sufficiently similar structures to the constructions in this paper.

Category / Keywords: foundations / Hash Functions, Indifferentiability, RO, Integrated-Key

Date: received 6 Jan 2012

Contact author: s alkuwari at bath edu

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Version: 20120107:160008 (All versions of this report)

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