Electronic apparatus, method, and storage medium

A method executed by an electronic apparatus comprising a controller including an instruction executer, a non-volatile memory, and a volatile register, the method comprising:

• generating or outputting data by the instruction executer;
• accepting a request for time stamp issuance for the data and issuing a time stamp;
• updating a first counter value for managing an order of the data according to a first operation of the electronic apparatus;
• and
• updating a second counter value for managing an order of the data according to issuance of the time stamp,
• holding the first counter value and a secret key in the non-volatile memory, and
• holding the second counter value in the volatile register, not in the first non-volatile memory, wherein
• the time stamp is a message authentication code or a digital signature issued from the first counter value, the second counter value, and the data using the secret key.

A non-transitory computer-readable storage medium having stored thereon a computer program which is executable by a computer of a controller in an electronic apparatus, the computer program comprising instructions capable of causing the computer to execute functions of:

• generating or acquiring data by an instruction executer included in the controller;
• accepting a request for time stamp issuance for the data and issuing a rime stamp;
• updating a first counter value for managing an order of the data according to a first operation of the electronic apparatus;
• and
• updating a second counter value for managing an order of the data according to issuance of the time stamp,
• holding the first counter value and a secret key in a non-volatile memory included in the controller, and
• holding the second counter value in a volatile register included in the controller, not in the first non-volatile memory, wherein
• the time stamp is a message authentication code or a digital signature issued from the first counter value, the second counter value, and the data using the secret key.