A Note on Provably Secure Double-Block-Length Hash Functions in a Black-Box Model

摘要

In this article, double-block-length hash functions with the rate 1/2 are presented which are optimally collision-resistant in the black-box model, that is, the time complexity of any collision-finding algorithm for them is Q(2e/2) if the underlying block cipher is random, where ? is the output length. They are composed of block ciphers whose key length is twice larger than their block length. Thus, following the construction given here, we can implement secure hash functions with 256-bit output using the AES with 256-bit key length.