How Secure are Locks and How They Work?
All of us have been locked out of our house, lost our keys, or forgotten to lock our door at one point or another, and each incident creates no small inconvenience. If during the morning commute I remember the front door isn't locked, 9 times out of 10 I'm turning back.
Locks are powerful objects to us. Even in an age when mind-blowingly complex algorithms and security schemes protect our online identity and information, we trust good ol' mechanical locks to protect our most valuable material possessions. Even as we get bored by our ability to go anywhere and do anything in an instant through cyberspace, we still treat a locked door as an impassable barrier in just about every situation.
So how secure are locks really? While the answer obviously depends on the specific lock in question, the truth of the matter is most locks around us are woefully ineffective against a skilled attack from a trained professional or unfortunately, a determined criminal. This applies to everyday front door knobs and deadbolts, and to furniture locks even more so.
To understand how secure locks really are, we have to spend a little time understanding how they work.
How do locks work?
The vast majority of locks around us are pin and tumbler locks, whose progenitor first appear in ancient Mesopotamia around 4000 years ago. They depend on a set of pins of varying length to stay locked until the right key is inserted.
Pin and tumbler locks consist of a stationary housing (also called a bible) and a rotating plug, which turns with the key. A set of pins live inside holes in the housing and the plug, and they prevent the plug from rotating without the correct key inserted. Pins that come in contact with the key are called key pins, and the pins that sit on top of them are called driver pins. These pins are numbered, with the one closest to the keyway entry referred to as pin #1. Finally, a very light spring pushes on each driver pin.
All the driver pins of a pin and tumbler lock are the same length, while the key pins vary in length. The varying lengths of key pins is what makes one lock unique compared to others of the same model, and represent the passcode, or bitting of the lock. As you may surmise, the serrations on the key matches up to the lengths of the key pins. When the correct key is inserted, all driver pins are lifted up to what’s called the shear line - the interface between plug and housing. As driver pins are no longer impeding the plug, it is free to rotate when the key is turned.
It turns out these pins are fairly easy to manipulate without a key. There are many different techniques. One can manipulate the pins one at a time (single pin picking) or many at once in rapid succession (raking) or use a bump key, to name a few. Recently I made a little video highlighting how easy it is to rake a padlock open. Although the transparent padlock in the video has poor tolerances and is very easy to open, most locks aren't far off to the trained locksmith.
Here is the video: