Viktoria: A New Architecture for Hash Functions

Abstract

Hash functions are increasingly playing an important role in contemporary cryptography. These functions are used to generate and verify digital signatures, to generate cryptographic keys, to generate pseudo-random bits, among other applications. The SHA-3 competition, sponsored by NIST (National Institute of Standards and Technology), has sparked new interest in research into new types of hash functions. New paradigms must withstand the increasingly technical and fast attacks of cryptoanalysis. In this paper we present a new paradigm for building a robust hash function, based on a permutation routine that builds its own randomness as it progresses through reading the message and transforms it into a compact 512-bit code (it can also be a larger hash). The new paradigm features two major innovations: fast preprocessing that initiates an internal state of 256!² permutations, and post-processing that guarantees a minimum number of executed rounds of the order of 2¹³. In the preprocessing it is possible to differentiate nearly identical messages very quickly and the post-processing brings an extra security to the final hash, coming from a large but indeterminate number of rounds. This paper presents the main characteristics of this new paradigm for building hash functions.