A method and apparatus is disclosed for synchronizing files stored in memory of two remotely located systems. The system can generate a copy of a source file at the destination location without transferring all the data of the source file. The destination location includes a reference file that can contain similar data as that contained in the source file. The synchronization is accomplished by sending keys (representing reference blocks of data from the reference file) to the source system. At the source system, a portion of each keys called a Feature is compared with portions of source file. If the Features match, a checksum corresponding to the reference block is compared with a check sum corresponding to the source block. If the checksums match, an short message identifying the key and reference block that matched is transmitted to the destination system in order that the reference block can be copied from the reference file in order to build the synchronized file.