Patent ID: 7457959

Claim:
A method for archiving digital records which allows the existence and content of a stored record at a point in time to be proven, while supporting a deletion mechanism which, if applied to the stored record, does not allow its existence to be proven even if the content of the stored record is guessed correctly, the method comprising: for each record in a set of records: determining a content fingerprint based on content of the each record; choosing a number that is distinct from the content fingerprint; determining a record identifier for the each record based at least in part on the number; and storing the each record and the number; selecting a plurality of records from the set of records; constructing a cryptographic hash for each record of the plurality, based at least in part on both the content fingerprint of the each record and on the record identifier for the each record; storing a timestamp record that comprises the cryptographic hashes constructed for each record of the plurality; determining a content fingerprint from the contents of the timestamp record; recording the content fingerprint for the timestamp record in a manner that allows both the time of the recording and the value of the content fingerprint at the time of the recording to be later proven; and deleting from storage a one of the plurality of records and also deleting from storage the number of the one record deleted; wherein the choosing of a number is done in a manner designed to make it impracticable to reconstruct or guess the number if the number has been deleted from storage.