According to a method of generating a key of the present invention, a first device and a second device are first brought into contact with one vibrator. In this state, the vibrator generates vibration. A first acceleration sensor provided in the first device and a second acceleration sensor provided in the second device detect the vibration. Subsequently, the first device notifies the second device of a first feature value based upon the detection result of the first acceleration sensor. The second device notifies the first device of a second feature value based upon the detection result of the second acceleration sensor. Then the first device compares the notified second feature value with the first feature value and generates a key based upon the comparison result. The second device compares the notified first feature value with the second feature value and generates a key based upon the comparison result.