A key having profile features which include a shaped indentation (74) on a first side of the blade (64) and an aligned projection (72) on the opposite side of the blade cooperates with a cylinder lock with unauthorized key trapping capability. The lock has an auxiliary locking pin (50) which cooperates with the key indentation and a movable plate member (34) which cooperates with the key projection. Both the indentation and projection must be present and properly sized and shaped for a properly bitted key to operate the lock.
