An information terminal that decrypts sealed data without returning program data after update to the state before update. The information terminal includes update certificate storage unit storing an update certificate for certifying update of the program data to be executed by CPU, and a selection unit which, when the CPU is to execute program data, judges whether or not digest of the post-update program data in the update certificate matches digest of the program data to be executed, and selects digest of the pre-update program data in the update certificate when it judges that they match. The CPU executes the post-update program data. The information terminal further includes a security device that stores an extend value of a program data digest when the pre-update program data is executed by the CPU according to a request from the selection unit.