Patent ID: RE39458

Claim:
A method of transmitting data from a source file located at a sending computer to a receiving computer, the computers being connected through a computer data interface, the method comprising the steps of: (a) dividing a reference file located at the receiving computer into a plurality of data blocks, each data block having a length of n bytes, and associating each data block with a reference key value determined in accordance with a key defining method by the data in that block; (b) transmitting the reference key values to the sending computer; (c) identifying blocks of data of length n bytes from the source file, determining source key values in accordance with the key defining method, and using the source and reference key values to compare blocks of data from the reference file to blocks of data from the source file and, in instances where a match is found between a block of data from each file, sending an indication of the match to the receiving computer so that the block of data indicated by the match need not be transmitted to the receiving computer.