US Patent 7752171 Efficient computer file backup system and method

A system and method for efficiently backing up and restoring computer files to a central storage system. A hashing key is computed for each file to be backed up on a target computer. The hashing key is compared to a list of hashing keys stored locally to see if the local file has been previously backed up. If the hashing key is not listed locally, then the hashing key is compared to a list of hashing keys of centrally backed up files. Only if the hashing key is not present in both the local and the central list is the file backed up. Backed up files may be renamed to their hashing key for further efficiencies.