Controller system

A controller system, comprising:

• a processor, configured to acquire, by turning on the controller system, a control program from a server in which the control program is stored;
• a volatile storage device that stores the control program acquired while electric power is supplied to the controller system and erases the control program by stopping supply of the electric power to the controller system;
• and
• a non-volatile storage device that non-volatilely stores a first hash value generated from previously executed control program, wherein
• the processor is further configured to:
• execute the control program stored in the volatile storage device,
• generate a holding variable that is a variable for holding a state of the controller system, and upload the holding variable to the server when the controller system shuts down, wherein
• when controller system is restarted, the processor acquires the holding variable together with the control program and a program ID associated with the control program from the server through encrypted communication with the server, and
• generates a second hash value including the control program, the program ID, and the holding variable, verifies the control program and the program ID have not been tampered with and stores the control program in the volatile storage device when the generated second hash value matches the first hash value stored in the non-volatile storage device.