History
In the 1970s, locksmiths in Denmark shared a
technique for knocking on a lock cylinder while
applying slight pressure to the back of the lock
plug. When the pins would jump inside of the
cylinder, the plug would be able to slide out
freely, thus enabling the locksmith to disassemble
the lock quickly. The use of a bump key was not
introduced until some time later and was first
recognized as a potential security issue around
2002–2003 by Klaus Noch who brought it to the
attention of the German media. After further
examination of the procedure, a white paper was
drafted in 2005 by Barry Wels & Rop Gonggrijp of The
Open Organization Of Lockpickers (TOOOL) detailing
the method and its applicability. A patent exists
for a lock device following the same principle as
the bump key from 1926–1928.
The technique then attracted more popular
attention in 2005 when a Dutch television show,
Nova, broadcast a story about the method. After the
method received further publicity from TOOOL
presentations at security conference talks, members
of TOOOL and a Dutch consumer group, Dutch
Consumentenbond, analyzed the capability of the
method on 70 different lock models and with trained
and untrained users in a 2006 study.
At the same time, Marc Tobias, an American
security expert, began to talk publicly in the
United States about the technique and its potential
security threats. In 2006, he released two further
white papers regarding the technique and its
potential legal ramifications.
When the correct key is inserted, the
gaps between the key pins (red) and
driver pins (blue) align with the edge
of the plug, called the shear
line(yellow)
Mechanics
A pin tumbler lock is composed of a series of
spring-loaded stacks called pin stacks. Each
pin stack is composed of two pins that are stacked
on top of each other: the key pin, which
touches the key when it is inserted, and the
driver pin, which is spring driven. When the
proper key is inserted into the lock, all of the key
pins and driver pins align along the "shear line,"
allowing the cylinder to turn. That is, when the
bottom of the driver pins and, therefore, the top of
the key pins form a straight line, the cylinder can
be turned, thus rotating the key pins away from the
driver pins. When no key or the wrong key is in the
lock, pin misalignment prevents the cylinder from
turning.
When bumping a lock, the key is initially
inserted into the keyway one notch (pin) short of
full insertion. Bumping the key inward forces it
deeper into the keyway. The specially designed teeth
of the bump key jiggle all of the pins in the lock.
The key pins transmit this force to the driver pins.
Because the pin movements are highly elastic, the
driver pins separate from the key pins for a split
second and are then pushed back by the spring. Even
though this separation only lasts a split second, if
a light force is applied to the key, the cylinder
can be turned and the lock can be opened while the
driver pins are elevated above the keyway.
Countermeasures
Lock designs
High-quality locks may be more vulnerable to
bumping unless they employ specific countermeasures.
More precise manufacturing tolerances within the
cylinder make bumping easier because the pins move
more freely and smoothly. Locks made of hardened
steel are more vulnerable because they are less
prone to damage during the bumping process that
might cause a cheaper lock to jam.
Locks having security pins (spool or mushroom
pins, etc.)—even when combined with a regular
tumbler mechanism—generally make bumping somewhat
more difficult but not impossible. Electronic locks,
magnetic locks, and locks using rotating disks are
not vulnerable to this attack.
Because a bump key must have the same blank
profile as the lock it is made to open, restricted
or registered key profiles are much safer from
bumping, since the correct key blanks cannot be
obtained legally without permission or registration
with relevant locksmith associations. While this
would make it harder to obtain key blanks, regular
keys can be filed down to act as bumpkeys.
Locks that have trap pins that engage when a pin
does not support them will jam a lock's cylinder.
Another countermeasure is shallow drilling,
in which one or more of the pin stacks is drilled
slightly shallower than the others. If an attempt
were made on a lock that has shallow drilled pin
stacks, the bump key will be unable to bump the
shallow drilled pins because they are too high for
the bump key to engage.
Lock brands with bump
proof design
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Other countermeasures
Pickbuster
is an aftermarket lock bumping countermeasure in the
form of a liquid gel which fills the cylinder
serving to dampen the kinetic energy of the bump
attack and prevent the key pin separating from the
driver pin. This solution has recently been tested
by ERA with positive results, and is undergoing
extended testing by the
Institute of Certified Locksmiths. However, this
solution is thought by many to attract dust and
grit, resulting in a jammed lock.
Bump Key Legal status
In the United States, bump keys fall into the
category of burglary tool in most states,
although only California specifically lists bump
keys in their
Penal Code. The burglary tool designation
requires that a police officer prove both possession
and intent to use the tool in a burglary for a
successful misdemeanor conviction. In California,
Governor
Arnold Schwarzenegger signed a bill (SB 1554) by
State Senator
Robert Dutton which specifically added the bump
key to the Penal Code.
In Delaware,
Delaware General Assembly Representative
J. Benjamin Ewing has introduced a bill (HB 396)
that defines a bump key as a burglary tool.
In other countries although less common, is also
illegal to do, and many bills were presented, and
could be prosecuted if caught.
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