INFORMATION TERMINAL, SECURITY DEVICE, DATA PROTECTION METHOD, AND DATA PROTECTION PROGRAM

摘要

Even if program data is updated, it is possible to decode the data sealed with the configuration before the update without restoring the updated program data into the original data. An information terminal includes: an update certificate storing unit (102) which stores an update certificate which certifies the update of the program data to be executed by a CPU (101); and a selection unit (103) which judges whether the digest of the program data after the update indicated by the update certificate of the program data is identical to the digest of the program data to be executed when the CPU executes the program data and selects the digest of the program data before the update in the update certificate if they are identical. The CPU (101) includes a security device which executes the program data after the update and holds the accumulated value of the digest of the program data when the program data before the update has been executed.