Patent ID: 7844774

Claim:
A method of operating a content-addressed storage system having a storage in which a client stores content of an item in the storage at a location determined by an address, the method comprising: (a) at a location of the client, generating an address from a list of fingerprint functions by using each fingerprinting function on the list to generate a fingerprint from the entire item content and forming an ordered list of the generated fingerprints to produce the address, the list of fingerprint functions including a plurality of different fingerprinting functions; (b) presenting the address to the storage system; and (c) based on the address, storing the item content in the storage, wherein the list of fingerprint functions represents an extensible fingerprint function having a current generation, the extensible fingerprint function defined in terms of earlier generations of extensible fingerprint functions, and wherein the ordered list of the generated fingerprints represents an extensible fingerprint at the current generation, such that it is possible to identify an extensible fingerprint of an immediately earlier generation from the extensible fingerprint of the current generation without having access to the item content.