Schneier on Security

Clive Robinson • December 20, 2011 5:48 AM

I’ll make my usual comment,

All mechanical locks have “slop” or “play”, they need it otherwise they would “bind” whenever the sun shines or the frost bites or a bit of dirt or even grease gets in the works.

Where ever there is play you have a crack into which you can drive the tip of an attack, be it just to “feel” or “impression” or to get in “picks” or “shims” and as we also know give it a good smack with a hammer to make use of “Newton’s Cradle” effect to “bump” the tumblers/pins.

It might only be a couple of thou’ (0.04-0.08 mm) in a good lock or 20-50 thou in a bad or worn lock. But you can get metal foil shims for measuring etc in even those smaller amounts of slop made out of some quite high tensile materials that don’t have the maliabality of softer metals such as steel or aluminium.

And guess what you can get shims made of glass for measuring very small gaps, that are flexible enough to slide down the side of the hasp to allow a snap lock to be worked…

I’ve even seen someone impression a lock key with a splinter thin length of hard wood, and I’ve made a “pick/rake gun” with a free metal coat hanger from a dry cleaners and a hammer and pair of pliers.

I’ve also been told you can fold up the old style metal foil around chewing gum to work a lock.

But my favourite tools used to be the plastic tooth pick and thin metal forceps/tweesers in a “Swiss Army Knife” for opening most padlocks and some of the cheap pinlocks used on office doors.