Untitled

Abstract

This paper uses a variant of the notion of inaccessible entropy (Haitner, Reingold, Vadhan and Wee, STOC 2009), to give an alternative construction and proof for the fundamental result, first proved by Rompel (STOC 1990), that Universal One-Way Hash Functions (UOWHFs) can be based on any one-way functions. We observe that a small tweak of any one-way function f is already a weak form of a UOWHF: consider the function F(x, i) that returns the i-bit-long prefix of f (x). If F were a UOWHF then given a random x and i it would be hard to come up with x = x such that F(x, i) = F(x , i). While this may not be the A preliminary version of this paper appeared as "Universal One-Way Hash Functions via Inaccessible Entropy" in EUROCRYPT 2010 [9].