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

We present a binary tree based parallel algorithm for extending the domain of a universal one-way hash function (UOWHF). For image, our algorithm extends the domain from the set of all n-bit strings to the set of all image-bit strings, where m is the length of the message digest. The associated increase in key length is image bits for image; image bits for image and image bits for image.