Patent ID: 7953977

Claim:
A method for restricting multiple uses of signed data while updating a security device having a nonvolatile storage unit including a master counter storage unit and a counter integrity register unit, the method comprising: using a computer processor to store a counter array; coupling a signature key hash value with a signature number counter wherein the signature number counter counts the number of signatures performed by use of the signature key; reading the counter array out of an external nonvolatile storage unit provided outside of the security device; storing the counter array in a volatile storage unit; reading the counter array stored in the volatile storage unit; reading the master counter storage unit; generating a present hash value from a value of the master counter storage unit and the counter array; reading a previous hash value stored in the counter integrity register unit; comparing the present hash value and the previous hash value; calling a signature function and updating the master counter storage unit upon determination that the counter array in the external nonvolatile storage unit has validity as a result of agreement of the present hash value and the previous hash value; newly generating a hash value by the hash function unit; and storing and updating the new hash value in the counter integrity register unit.