In a method of controlling an electronic device using a wearable device, the electronic device is paired with the wearable device. A cryptographic key, which corresponds to the electronic device, is stored in a secure storage device included in the wearable device. A distance between the wearable device and the electronic device is estimated by the wearable device. An unlock signal including the cryptographic key, which is stored in the secure storage device, is transmitted from the wearable device to the electronic device when the estimated distance is smaller than a threshold distance. The electronic device is unlocked based on the unlock signal.