Patent ID: 7587617

Claim:
A method by which a client connected to a network deposits data items into persistent storage, relying on a public data repository connected to the network for storage of data items that duplicate data already stored there and storing non-duplicate data items in a private data repository, the method comprising: determining a digital fingerprint of a data item that uniquely identifies the content of the data item; testing for whether an identical data item, identical in content with the data item, is already stored in the public repository by comparing the digital fingerprint of the data item to the digital fingerprints of data items already stored in the public repository; and if an identical data item is already stored in the public repository, creating an access authorization credential for the public repository associating the client with the identical data item and relying on storage of the identical data item in the public repository; and if an identical data item is not already stored in the public repository, depositing the data item in the private repository; wherein data items already stored in the public repository were transmitted to the public repository by clients of the public repository; wherein at least some clients of the public repository cannot access data items stored in the private repository; wherein access authorization credentials for the public repository are credentials that allow the client to retrieve data items from the public repository; wherein the digital fingerprint of the data item is a cryptographic hash of the content of the data item; wherein the client determines that some data items will be deposited only in the private repository based at least in part on the absence of identical content in the public repository, and wherein the client determines that some data items will be deposited in the public repository based at least in part on the presence of identical content in the public repository.