High Security Locks
There appears to be some confusion among consumers regarding pin-tumbler high security locks. To help dispel this confusion, I have written this post. In order for a lock to be considered a high security lock, it needs to offer the four following features.
Firstly, it must offer key control. This feature allows the owner of a high security lock to limit and monitor the generation of operating keys for his or her lock. The goal of key control is to protect the bitting information of the operating key, limit the availability of key blanks, and track the control keys in circulation. This is accomplished by the use of what are called Security Cards (or Key Cards). When a high security lock is purchased, the purchaser is issued one of these cards and must present it each time he or she requires a new key be generated for his or her lock.
Secondly, it must offer a very high number of key differs. Key differs are the number of possible keys that can be cut for a particular lock. The higher the number of key differs for a particular lock the more unlikely uncontrolled cross keying (i.e. the condition under which two or more keys accidentally operate the same lock) becomes. A Weiser WR3 key, a common residential key, for example, has 100,000 theoretical keying possibilities, Schlage Primus, a popular high security key, on the other hand, has 4.6 billion theoretical keying possibilities.
Thirdly, it must be able to resist forced entry techniques such as drilling, prying, and wrenching, among others. To resist drilling attacks, most high security locks are made with hardened steel pins, plates, and/or bearings. And to resist prying and wrenching attacks, they are made with a heavy-guage tubular housing and come with high-tensile steel mounting bolts.
Finally, a high security lock must be manipulation resistant. In other words, it must be able to resist picking, bumping, and impressioning attacks. A high security pin-tumbler lock typically thwarts picking attempts by using mushroom, spool, and serrated top pins; and by having a para-centric, restrictive keyway. These locks resist bumping attacks by incorporating at least one of the following technologies: shadow drilling, top gapping, trap pins, auxiliary locking mechanisms, or non-pin mechanisms. Shadow drilling involves the drilling of one pin chamber higher than the others. Top gapping refers to the use of tapered driver pins. Trap pins are pins that fire when a plug (or cylinder) is rotated without the operating key. And auxiliary locking mechanisms involve the use of slider pins, floating pins, and blocking pins. Finally, high security locks prevent impressioning (i.e. the process of making an operating key for a lock without dismantling it) by tracking and restricting the availability of key blanks.
Examples of popular high security pin-tumbler locks in use today include: ASSA, Medeco, Schlage Primus, CX-5, Tul-T-Lock, and Abloy. These locks all offer strict key control, are able to resist a wide variety of forced entry techniques, and are manipulation resistant.