ELECTRONIC KEY SYSTEM

An electronic key system includes a door unit, an installed device, a portable device, at least one processor, and a storage medium storing. The storage medium stores a program that causes the processor to execute a composite authentication process and a simple authentication process. The composite authentication process permits unlocking of the door unit if all of the following conditions are satisfied: key information output from the portable device matches pre-registered key information; a user's motion matches pre-registered first motion information; and the motion matches pre-registered second motion information. The simple authentication process is executed during the time from locking of the door unit to elapse of a preset time or from locking of the door unit to when the portable device is located outside an authentication notification area. The simple authentication process permits unlocking of the door unit if the key information matches the pre-registered key information.