Bump a Lock

From Wired How-To Wiki

Picture Courtesy Robert Scales via Flickr

Feel safe behind your locked door? Sorry to spoil your sense of security, but there's an old lockpicker's secret anyone could learn to make a skeleton key and open almost any locked door.

"Bumping" is a method for picking a lock using a filed-down key of the appropriate type and tapping on the cylinder. This causes the pins to drop into place as if the correct key was being used. The technique is named after the bumping motion used to knock the pins into place.

Why is this something you need to know? According to TOOOL, The Open Organization of Locksmiths, 95% of lock models in America are vulnerable to bumping. Of course, lock manufacturers have a vested interest in keeping this vulnerability a secret in the vain hope it won't get exploited. For many years they wouldn't even talk about it with other locksmiths. Only recently was bumping formally announced to the world, during the 2006 Hackers on Planet Earth (HOPE) Conference. Ever since, lock companies were forced to come clean.

Now, you could trust your home's lock security hoping thieves don't read this article, or you could learn the attacks yourself and make sure your lock is up to snuff.

The Steps to Bumping a Lock

1. Identify the model of lock you're trying to bump.
2. Create a bump key. Any key template designed for your model of lock will work, as only the teeth are different. Turn your key template into a bump key by asking a locksmith to lathe the key down to its maximum depth; this is called a 999 key. A law-abiding locksmith might be wise to your lock-bumping plan and refuse. Alternatively, you can file it down yourself.
   

   Photo Courtesy RobotSkirts via Flickr
3. Get Bumping! Insert the bump key in the lock, then strike the back of the key with a hard object, for example the handle of a screwdriver or, ideally, a rubber mallet. If you get your timing right, you'll be able to turn the cylinder approximately the same time as the bump occurs, opening the lock. While practice is necessary, the actual physics won't challenge you much.

It might sound difficult, but even kids can bump locks once they are shown how it's done.

Resources

A YouTube video with a demonstration of lock bumping follows.

Pickbuster is an aftermarket product, a solution that is injected into the lock cylinder that prevents the pins from dropping down during bumping.

Master Lock's informational video about its Bump Stop Security Products and its Bump Stop web page.

TOOOL's Web Page and a PDF description of the bumping process.

Legal Issues

Note that in some areas, bump keys count as burglary tools, and possession of one can be a misdemeanor offense.