Locking a Dead Man's Chest

If you have valuables you don't want stolen, it's important to have a good lock. Locks are really just puzzles designed to slow up the thief for long enough that they will be caught in the act, give up or not try in the first place. Some locks use keys - like Davy Jones' Dead Man's Chest in the Pirates of the Caribbean, to protect his heart from the likes of Captain Jack Sparrow. As Davy Jones discovered, the problem with keys is they can be stolen or copied, and with practice they can be picked. Combination locks can easily be opened too ... if you have enough time. You just try all the combinations! Back in the middle ages the French peasantry used a rather ingenious sort of lock called a "baguenaudier" ("time-waster"). It was really just a simple puzzle, but one that took a long time to solve ... even when you knew the answer. Maybe it would have been a better way to lock a Dead Man's Chest.

We've recreated a version of the French Peasant's lock that doesn't take too long to open if you know how. Open the lock to get at our treasure inside the chest. The lock has a small window through which you can swap in and out the circular discs switching them for special T shape pieces. You can only swap the one currently in the window (click anywhere on the bolt), and only if it's not held in place by the adjacent disc overlapping it. The bolt will slide left and right. If you manage to slide it all the way out of the right hand side then the chest will spring open. Try it straight away and you will see that at the start it won't go. There is a T piece at the end blocking it from sliding. T pieces are too big to slide out the end.

The only way to get it out is to swap the Ts for discs. Trouble is you can only do that if they are not held in place by an adjacent overlapping disc. That means you have to swap in Ts to free them! But then they stop the bolt sliding out. Arghh!

Can you solve the puzzle and crack the lock?

Just in case you need it we've provided a special cracker tool. When switched on (click "show cracker") it reveals the innards of the lock and better still reveals the secret code sequence needed to solve the puzzle ... if you can work out how to use it. Speed is of the essence if you are to raid the chest before the peasants return and run you through with a pitchfork. To be an expert (not to mention a living) lock cracker you should do it not only in as few swaps of discs and Ts as possible but in as few turns (slides or swaps) as possible.

Once you've solved it (or given up on the treasure) read on to find more about the code the cracker is revealing, what it has to do with the way computers store numbers and discover it's link to modern day digital TV.

The lock puzzle only works with some web browsers. If it does not load properly for you, either try a different browser or download this version you can run directly on your own computer.