Construction of universal one-way hash functions: Tree hashing revisited

Abstract

We present a binary tree based parallel algorithm for extending the domain of a universal one-way hash function (UOWHF). For t ⩾ 2 , our algorithm extends the domain from the set of all n-bit strings to the set of all ( ( 2 t - 1 ) ( n - m ) + m ) -bit strings, where m is the length of the message digest. The associated increase in key length is 2 m bits for t = 2 ; m ( t + 1 ) bits for 3 ⩽ t ⩽ 6 and m × ( t + ⌊ log 2 ( t - 1 ) ⌋ ) bits for t ⩾ 7 .