A New Paradigm for Collision-free Hashing: Incrementality at Reduced Cost

We present a simple, new paradigm for the design of collision-free hash functions. Any function emanating from this paradigm is <i>incremental.</i> (This means that if a message x which I have previously hashed is modified to x' then rather than having to re-compute the hash of x' from scratch, I can quickly ``update'' the old hash value to the new one, in time proportional to the amount of modification made in x to get x'.) Also any function emanating from this paradigm is parallelizable, useful for hardware implementation.