Bump Keys

Harold Fink, Locksmith, CRL CPS
Sun, Jan 31, 2010

Bump Keys

Bump keys are a very real security threat because they work

How Bump Keys Work

Bump keys are a very real threat, and are easily obtained on the internet. A bump key, when used effectively, will create a separation between the bottom pins and drivers in a pin tumbler lock, allowing the cylinder plug to turn. How bump keys work is the key is cut to all 9’s, or the deepest cuts called for in that particular manufacturer’s specifications. The key is then put in the keyway and positioned not quite against the cylinder plug, is tapped on the bow of the key while tension is being applied to the cylinder plug, and that separation between bottom pins and drivers is allowed to occur. The plug is allowed to turn and the locking mechanism of the door can be actuated as if the operating key were being used.

Bump keys are a hot topic on the internet and many videos can be found which are often quite inaccurate and misleading. There are even ads which claim that a product can be sprayed into the keyway to render the lock bump key proof. It is not so simple to just spray some magic solution into the keyway and render the standard pin tumbler design lock bump key proof. Bump keys have been around long before the internet and are a very real security threat. Bump keys are a very real security threat because they work. More importantly, bump keys are a very real security threat because it is so easy to obtain information about bump keys and find bump key suppliers on the internet.

Bump Key Resistant Locks

With a standard pin tumbler cylinder, it is possible to make the lock much more bump resistant by taking some consideration in what length of bottom pins are used when pinning up the cylinder. The standard pin tumbler design cylinder could be pinned up with at least one or more cuts slightly deeper than the 9 cut in the manufacturer’s specifications. Because most bump keys would be cut to all 9’s (ok 0 with Sargent), the bump key would cause at least one bottom pin to extend up past the sheer line no matter how effectively it is used, preventing the plug from turning. This does not render the lock bump key proof, but makes it nearly impossible for most bump keys that would be found on the internet to work. If you find bump keys on the internet and try them on cylinders pinned up in this manner, those bump keys probably will not work. Pinning up cylinders out of manufacturer’s specifications is a bad idea, even if it means stopping bump keys, but I had to mention it because it is possible to pin up a standard pin tumbler cylinder in such a way as to render it bump key resistant. Additionally, use of spool drivers has long been a way to provide much more picking resistance, and bump key resistant locks can be offered to your customers by using at least one or two deep cuts and spool drivers. Spool drivers, when installed properly in the cylinder housing, will tilt when they pass along the sheer line while tension is being exerted against the plug, and prevent any further movement of the bottom pin pushing up against that driver. This will render that cylinder much more bump key resistant. If spool drivers were used in every position in a 6 pin tumbler design, and the cuts in the operating key are not all deep 9 cuts, this would be one method to provide bump key resistant locks to your customers.

Bump Key Proof Locks

High Security locks that utilize secondary locking mechanisms such as Medeco, Mul T Lock, or ASSA are a good example of what I would call bump key proof locks. The engineering of the cylinders and deadbolts produced by any of these companies is far superior to what is available in standard pin tumbler designs, and you have the added benefit of key control. With high security, bump key proof locks, you not only render the bump key useless, but have the peace of mind that comes with knowing that no one can duplicate your keys without your approval. It really is worth the extra money to install high security locking hardware on your most vulnerable doors. The extra attention given to the installation of these locks usually results in a far superior strike in the door frame, and may even prevent the deadbolt from being forced out of the strike, effectively stopping brute force attacks on the door as well. Bump keys are not going away, and as valuable a resource as the internet is, it can often lead to some sensitive information being broadcast to the public that locksmiths would have kept to themselves in the past. Bump key sellers are now so plentiful that our role as security professionals has to include educating the public of the very real threat of bump keys and how bump keys work.