New  Anti-Bump  Technology
from  Master Lock  By  Billy  Edwards, CML

The Bump Keys we know today have had a few different names since they were invented in 1925. Nine keys or 999 keys has been a very popular name and there have been others. Until about two and a half years ago they were a well kept secret within the locksmith trade. They were such a well kept secret that prob- ably as much as 75% of locksmiths had never heard of them.

There have been a number of patents granted in the US and else- where through the years for methods to prevent bumping. Some of those methods added some significant complexity to the inline pin tumbler mechanism and many of them just simply didn't work in real life.

This secrecy has actually been a problem since this information has been available on the web. It has been a problem because locksmiths who are not familiar with the technique don't believe it can work. Some of those locksmiths have been vocal about their disbelief and even tried to demonstrate that it doesn't work. It is a shame that the inability of some in our trade reflects badly on all locksmiths. It reflects badly because when the public can see videos on the web and their local TV demonstrating that it does in fact work we lose credibility.

For those who may not know, in 1925 George Baron was granted British Patent 251,810 for Bump Key Technology. He made Bump Keys as a kit which was sold to the trade. Over the intervening years the technique has been forgotten and rediscov-ered many times, most likely due to the secret nature given to it by locksmiths.

The action of the bump key has typically been thought to repli-cate the effect of a pick gun or be similar to the executive desk toy shown above. However, we thought that we needed to know for sure so we arranged for high speed photography which shows that there is a different effect. When used as designed a pick gun applies force to the bottom pin and that force is transferred to the top pin 
which then travels above the shear line. 

The bump key impacts the bottom pin and then, via the ramp formed by the steeple between cuts, pushes the entire pin stack vio- lently upward. When the pin stack reaches the zenith of its rise in the chamber the bot- tom pin descends and separates from the top pin before the top pin starts to descend. The gap between the two pins crosses the shear line and the slight torque being applied to the key' causes the plug to rotate.

There are two different meth-ods that can be used to make bump keys and the keys produced are used in different ways. For lack of better names I call the two types of keys the PULL type and the PUSH type. The Pull type has every cut position cut to the deepest possible depth of cut and then another cut added at the tip of the key with the correct spacing as if there were an extra chamber. These cuts should be between .005" and .010" deeper than standard for an optimal effect. The Push type key has every possible cut position cut to the deepest possible depth, (plus that .005" or .010" extra), and then the shoulder(s) are cut back .040" to.060".

The Problem The problem of course is the significant compromise potential this type of attack presents. Now that the technique is available to the general public, and given the very short learning curve to master the technique, every in-line pin tumbler lock is at risk of immediate compromise.

In fact there have been a number of burglaries around the coun-try with no forcible signs of entry that could be attributed to Bump Keys. Many say that they aren't being used and, until someone is caught in the act or a true method of determining forensically they have been used, many won't believe they are a threat.

The Solution All of that hasn't deterred the lock manufacturers and many others who have been feverishly working toward finding a solution to this problem attack. A solution that will prevent it from working.

Master Lock embarked on a dedicated R&D effort in August, 2006 to develop a solution to meet three criteria: 1) Cylinder must retrofit into existing locks   2) Highly resistant to bump attacks   3) Cost effective

Our initial development was based on the inertia cradle model. We geared our solution toward that method of attack. The first thing we tried was a telescoping top pin. We even tried a couple of different designs for that pin. They didn't work! We thought it was the result of insufficient mass in the pin. It wasn't. We tried the second design for a telescoping pin hoping to equalize the mass in the halves. That didn't work either. The high speed video showed that the pin did-n't telescope at all because the action did not replicate what goes on in the inertia cradle.

Then it was on to other ideas. Magnetic pins were next. In theory a magnetic top pin with a steel bottom pin should be inseparable. They weren't! In all cylinders there is a shelf created between the pin chamber in the shell and the corresponding chamber in the plug because the chamber in the shell is typically larger to allow for some small end play that occurs in all cylinders. On the way back down the magnet isn't perfectly in line with the bottom pin and the edge of it hangs on that shelf. The extra mass in the steel bottom pin causes them to separate and the lock is bumped open.

Spool pins and using stronger springs were ineffective too. We also thought our EDGE key control product could resist bumping. If the dimple pattern wasn't correct it was bump proof, but ifyou have the correct dimple pattern you can eventually bump it.

Due to our lack of success we commissioned high speed video (2,162 frames per second) to better understand the dynamics of the lock bumping technique. After analyzing the video we changed design direction based on learning what really happens in the cylinder.

The first new idea was the shouldered pin with an oversized bore in the shell that didn't quite go all the way to the ID of the plug hole. In con-junction with a Short bottom pin there was a gap between the top pin and the bottom pin. Impacting the bottom pins with a bump key wouldn't cause the bottom pin to move the shouldered pin. Eureka! It worked. A cylinder that was roughly 90% bump resistant.

Now it was time to improve the result. Changing the shape of the top pin so that it had a taper proved to be about 97% resistant until 20 hits or so had been tried. It had the added benefit of being more economical to produce since counter drilling wasn't involved. Then the pin chamber started being distorted and the pin no longer wedged itself in place. The top of the chamber actually becomes beveled to match the pin shape and then it bumps much easier as well as letting simple torque sometimes cam the pin out of the plug. 

Time to change design. The solution was to reverse the taper on the end of the pin. The oversized tumbler diame-ter serves to keep the pin from fully entering the plug and the reverse taper also has the effect of improving stan-dard pick resistance, increasing the bump resistance to 99.99% and mak-ing bump attempts fully detectable.

Thus, the Master Lock Bump Stop technology became a reality. With this result, our objective was achieved.

The solution will be available as an option in keyed locks and cylinders. Pins will not be made available as a service part as they are only a component of the overall solution.

Now let's take a look at that detectability factor-offered by the new pin. By design we made the corner of the pin a sharp one and because the pin has very little side to side movement, when the lock is bumped the pin actually starts to serrate the inside of the pin chamber in the plug. This photo is slightly exaggerated because this lock had been bumped around 150 times without opening, but the pin starts to mark the plug with the first impact, easily detectable with micro-scopic analysis.

The sequence here reflects what happens inside the cylinder equipped with this pin when it is bumped. Notice that the new pin isn't moved in the bump process. This new pin design only needs to be in a single pin chamber to make the lock very bump resistant. That one location needs to be in the same chamber as a 0, 1 or 2 depth in Master Lock Padlocks or a 1, 2 or 3 in American Lock padlocks.

Master Lock has applied for patent protection on this new technology and will be mak- ing it available for use in all in-line pin tumbler products from padlocks to door locks. Initial padlock production will begin in June and will be available in the entire product line by October, 2007. Contact your distributor _ the Bump Stops here!