How to Choose a Lock that is Bump and Pick Resistant
Key Bumping Video
Key Bumping is a means of simple entry that requires little skill. A general rule of thumb, the cheaper the lock, the easier it is probably going to be to bump. Therefore, you tend to get what you pay for when shopping for a bump-resistant lock. Following are strategies you can use to inhibit or defeat key bumping.
Most Effective: Get a Totally Keyless Lock
Some mechanical or electronic locks do not use a key at all and therefore are completely immune to key bumping. The most secure example would be the Kaba Mas CDX-09 which uses a dial outside like a safe lock. Sargent and Greenleaf offers the "Brute" mechanical rim lock to compete with the CDX-09. The CDX-09 is an electronic lock that generates its own power, used widely in federal government applications.
Much cheaper are the Kaba Ilco 900, 6200, and 7100 series locks.
Security professionals know that anything that is put on with tools can be taken off with tools, but as far as key bumping goes, these locks offer no opportunity.
Effective: Get a Pick Resistant Lock
Pick resistant locks have an extra set of tumblers or locking apparatus so that in effect the key has to do two things at once. Because of their resistance to manipulation, these locks are also resistant to key bumping.
One of the most popular pick resistant locks is the Medeco. The pin tumblers in this lock must not only be raised to a certain level, they must be turned right or left or not turned at all in order to allow the key to turn. An effective set of bump keys would need to have several thousand variations of angles in order to turn the pins properly so that they could be bumped.
Mul-T-Lock cylinders use a pin-within-a-pin principal. Since the keys are drilled to precise depths to operate the pin tumblers, bump keys would be exceedingly difficult to make.
Another popular pick resistant lock is the Schlage Primus. This lock uses a second set of pins so that the key must do the job of 2 keys. This system is not quite as secure as the Medeco since the keys are similar within a geographical area. If a key bumper were to get the blank, they could conceivably make a bump key that would work.
This principal is similar to the one below. Both rely to an extent on luck.
Somewhat Effective: Get a Lock in an Uncommon Keyway
Shown in the illustration at right is the part of a lock cylinder called the 'keyway.' The keyway is the shape of the hole that will accept the key.
One way to inhibit bumping is to get a lock with a keyway the key bumper is not likely to have. Bump keys must be the same keyway as the lock or they won't fit in. If they won't fit in the lock, they can't be used to bump the lock.
If you get an odd enough keyway, the key bumper would perhaps have to take a photo of your lock, identify the keyway, get a blank, and then return to bump your lock. All of this adds risk to the act of key bumping, providing more chances to be caught or identified.