Abstract

We say a blockcipher-based hash function is highly efficient if it makes exactly one blockcipher call for each message block hashed, and all blockcipher calls use a single underlying key. Although a few highly efficient constructions have been proposed, no one has been able to prove their security. In this paper we prove, in the black-box model, that it is impossible to construct a highly efficient blockcipher-based hash function which is provably secure. Our result implies, in particular, that the Tweakable Chain Hash (TCH) construction suggested by Liskov, Rivest, and Wagner [3] is not correct under an instantiation suggested for this construction, nor can TCH be correctly instantiated by any other efficient means.

Citations