Patent ID: 7774610

Claim:
A method comprising: using a file system of a storage server to provide a user with access to data stored by the storage server; selecting a subset of the data stored by the storage server, the selected subset containing one or more data items, including at least one file; creating a signature file for the selected subset, the signature file specifying the data items contained in the selected subset and locations of said data items within the selected subset, the signature file further including metadata associated with each said data item, the metadata including a write once, read many (WORM) state indication for at least one data item in the selected subset; generating a cryptographic hash for each file in the selected subset and including each said cryptographic hash in the signature file in association with the corresponding file; using a private key of a public-private key pair to generate a first digital signature of the signature file as a whole; associating the first digital signature with the signature file; migrating the selected subset from a source set of storage media to a destination set of storage media; and using the signature file to verify the selected subset of the data, as stored in the destination set of storage media, including verifying a WORM state of the at least one data item.