A class of randomized strategies for low-cost comparison of file copies

A class of algorithms that use randomized signatures to compare remotely located file copies is presented. A simple technique that sends on the order of 4^flog(n) bits, where f is the number of differing pages that are to be diagnosed and n is the number of pages in the file, is described. A method to improve the bound in the number of bits sent, making them grow with f as flog(f) and with n as log(n)log(log( n)), and a class of algorithms in which the number of signatures grows with f as fr^f, where r can be made to approach 1, are also presented. A comparison of these techniques is discussed