Collision Resistance of the JH Hash Function

In this paper, we analyze collision resistance of the JH hash function in the ideal primitive model. The JH hash function is one of the five SHA-3 candidates accepted for the final round of evaluation. The JH hash function uses a mode of operation based on a permutation, while its security has been elusive even in the random permutation model. One can find a collision for the JH compression function only with two backward queries to the basing primitive. However, the security is significantly enhanced in iteration. For $c\leq n/2$, we prove that the JH hash function using an ideal $n$-bit permutation and producing $c$-bit outputs by truncation is collision resistant up to $O(2^{c/2})$ queries. This bound implies that the JH hash function provides the optimal collision resistance in the random permutation model

MJH: A Faster Alternative to MDC-2

Abstract. In this paper, we introduce a new class of double-block-length hash functions. Using the ideal cipher model, we prove that these hash functions, dubbed MJH, are asymptotically collision resistant up to O(2n(1−)) query complexity for any > 0 in the iteration, where n is the block size of the underlying blockcipher. When based on n-bit key blockciphers, our construction, being of rate 1/2, provides better provable security than MDC-2, the only known construction of a rate-1/2 double-length hash function based on an n-bit key blockcipher with non-trivial provable security. Moreover, since key scheduling is performed only once per message block for MJH, our proposal significantly outperforms MDC-2 in efficiency. When based on a 2n-bit key blockcipher, we can use the extra n bits of key to increase the amount of payload accordingly. Thus we get a rate-1 hash function that is much faster than existing proposals, such as Tandem-DM with comparable provable security. This is the full version of [19].

Concurso NIST. Análisis del concurso (2007-2012)

El objetivo de este proyecto es dar a conocer el concurso SHA-3, concurso que ha transcurrido durante los últimos años y que ha promovido el Instituto Nacional de Estándares y Tecnología, también conocido como NIST, con el objetivo de encontrar el nuevo algoritmo criptográfico de función resumen SHA-3 que se utilizará de estándar de aquí en adelante. Con este fin se ha realizado un estudio sobre criptografía en general y sobre algunos de los algoritmos criptográficos de función resumen existentes hasta el momento, además de un análisis detallado del concurso, de sus fases y de sus finalistas. Además se ha hecho un breve resumen de los problemas existentes en la actualidad referentes a seguridad y de los escándalos concernientes a ello de todos los tiempos en la sociedad norteamericana.Ingeniería Técnica en Informática de Gestió