Control device, security management system, and security management method

A central processing unit of a control device includes: a control calculation unit that performs calculation on the basis of storage content of a nonvolatile storage unit and controls a machine; an update unit that accepts operation input in a first maintenance mode or a second maintenance mode, which has a narrower operable range than the first maintenance mode, and updates the storage content of the nonvolatile storage unit in accordance with the operation input; a security management unit that determines permission or prohibition of the operation input in the first maintenance mode with the use of a hardware key; and a security management unit that determines permission or prohibition of the operation input in the second maintenance mode without the use of the hardware key.