A cylinder lock includes a shell and a plug inside the shell. A locking pin, a sensor pin and a flexible coupling are mounted within the plug. The sensor pin moves the flexible coupling and the coupling moves the locking pin to an unlocked position when the correct key is inserted into a key slot in the plug. The key includes a locking pin receiving notch, to allow the locking pin to move to the unlocked position. The key also includes a contact surface that moves the sensor pin and thereby moves the locking pin to the unlocked position through the flexible coupling. When an incorrect key, without the locking pin receiving notch, is inserted, the flexibility of the flexible coupling allows the sensor pin to move without moving the locking pin. The cylinder lock may also include conventional pin tumblers. The receiving notch of the key may be provided with an alignment surface that cooperates with the locking pin to control the depth the key is inserted into the lock and allow keys of varying length to align relative to the pin tumblers of the cylinder lock.