Patent ID: 8082231

Claim:
A method of representing a data segment comprising: receiving a list of one or more tokens representing one or more data portions included in the data segment; receiving a unique identifier uniquely identifying said data segment from other data segments; receiving a signature value determined using said list of tokens and said unique identifier by digitally signing said list of tokens and said unique identifier; storing said list of tokens, said unique identifier, and said signature value as information corresponding to said data segment at a first point in time; and performing processing at a second point in time subsequent to the first point in time to rebuild a bit map tracking changes for the data segment since said first point in time, said processing further including: performing first verification processing of said list of tokens using said unique identifier and said signature value; and if said first verification processing is successful, performing second processing for each data portion of the data segment at the second point in time, said second processing including determining a current token for said each data portion, determining whether the current token for said each data portion at the second point in time matches a first of the tokens from the list corresponding to said each data portion at the first point in time, and setting an entry in the bit map for said each data portion to zero (0) if the current token has a matching first token from the list at the first point in time and setting the entry to one (1) otherwise.