Patent ID: 7320009

Claim:
A computer-implemented method for comparing two versions of a file to determine the differences between the versions, the method comprising: obtaining a fine signature and a coarse signature for at least one segment of data of a base file; accessing a revised version of the base file; obtaining a segment of data of the revised version and calculating a coarse signature for the obtained segment of the revised version; determining whether the coarse signature for the obtained segment of the revised version matches the coarse signature for the at least one data segment in the base file; if a match of the coarse signatures is present, calculating a fine signature for the obtained segment of the revised version of the base file and comparing the fine signature to the fine signature for at least one data segment of the base file; if the fine signatures match, storing a fine signature for the segment of the revised version; if a match of the coarse signatures is not present, calculating another coarse signature for another segment of data of the revised version wherein said segment of data and said another segment of data of the revised version have a same resolution; comparing said another coarse signature for said another segment of data to said coarse signature for said at least one segment of data of said base file; and recursively repeating said calculating said another coarse signature and said comparing said another coarse signature to said coarse signature for said base file until a match, if possible, is obtained.