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Publication# Faster and Smoother - VSH Revisited

Abstract

We reconsider the provably collision resistant Very Smooth Hash and propose a small change in the design aiming to improve both performance and security. While the original proofs of security based on hardness of factoring or discrete logarithms are preserved, we can base the security on the k-sum problem studied by Wagner and more recently by Minder Sz. Sinclair. The new approach allows to output shorter digests and brings the speed of Fast VSH closer to the range of "classical" hash functions. The modified VSH is likely to remain secure even if factoring and discrete logarithms are easy, while this would have a devastating effect on the original versions. This observation leads us to propose a variant that operates modulo a power of two to increase the speed even more. A function that offers an equivalent of 128-bit collision resistance runs at 68.5 MB/s on a 2.4 CHz Intel Core 2 CPU, more than a third of the speed of SH A-256.

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Related concepts (32)

Related publications (34)

Cryptographic hash function

A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with a fixed size of bits) that has special properties desirable for a cryptographic application: the probability of a particular -bit output result (hash value) for a random input string ("message") is (as for any good hash), so the hash value can be used as a representative of the message; finding an input string that matches a given hash value (a pre-image) is unfeasible, assuming all input str

Collision resistance

In cryptography, collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b but H(a) = H(b). The pigeonhole principle means that any hash function with more inputs than outputs will necessarily have such collisions; the harder they are to find, the more cryptographically secure the hash function is.

Hash function

A hash function is any function that can be used to map data of arbitrary size to fixed-size values, though there are some hash functions that support variable length output. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. The values are usually used to index a fixed-size table called a hash table. Use of a hash function to index a hash table is called hashing or scatter storage addressing.

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Post-quantum cryptography is a branch of cryptography which deals with cryptographic algorithms whose hardness assumptions are not based on problems known to be solvable by a quantum computer, such as the RSA problem, factoring or discrete logarithms.This ...

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