PVC Cryptex Keeps Your Stuff Safe

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Apparently we’ve never shared a Cryptex before! Made popular (and coined) by the Da Vinci Code, a Cryptex is a combination style lock originally used to store secret messages. You can make your very own using a few pieces of PVC pipe, some epoxy, and nuts and bolts!

Cryptexes have a clever design that cannot really be lock picked, without simply breaking it. In [Dan Brown’s] novel, it was said that some Cryptexes stored a fragile vial of vinegar with the message written on papyrus — that way, if it was forcibly opened the vile would break, dissolving the thin papyrus note.

They work similar to a bicycle’s combination lock, where if the correct password is guessed, the tumblers inside align, allowing the two halves of the cylinder to come apart. It’s actually a very simple design on the inside, and the whole mechanism can easily be made by yourself with minimal tools.

Using PVC it’s a relatively easy project, although you could also make a much more impressive one out of metal instead, like this amazing one made from a copper pipe.

24 thoughts on “PVC Cryptex Keeps Your Stuff Safe

  1. And now someone will be making a Cryptex bruteforce cracking tool.

    Actually, that’d be really cool. I’d imagine that it would have bands that wrap around the individual rings connectd to servos or so.

  2. Is it susceptible to the same attacks as bike combination locks, where if you pull cord and then turn rings starting from the most tough to turn, you can crack it in seconds? My friends were really surprised when I opened unknown locks in seconds :D

    1. You’re not thinking deviously enough. A cryptex made to be really secure would be designed so that it would not have any give or slack or redistribute loads as rings are turned. Only when all the rings are correctly aligned would it open.

      More complexity could be added by having the first code release a plunger or other device that shifts the gates to a second combination.

      If you haven’t read the book, the Davinci Code movie left out a large chunk of story where there was a second cryptex inside the first one.

  3. “Cryptexes have a clever design that cannot really be lock picked, without simply breaking it. ”

    Yeah it can. Same as a bike lock. Pull and start turning one ring (usually the closest). When there is pressure on all rings equally, they will turn with the same resistance. When one has gotten to the unlocked position, that load will be distributed to the next highest binding ring and, if it is of high quality, all the other rings. Repeat until one ring is left. Give it a spin and it is open.

    The alternate with-tools method is to use a feeler gauge between the rings, attempting to probe for its ‘flat’, or the area on the ring that determines the unlocked position. Align them all, spin them together (as the index might not actually be the mechanical retention point) and it pops open.

    Same sort of thing can be applied to most any multi-ring lock, like briefcases and such. Sesamee style combination locks have a depress-able shackle and a locking plate to prevent this type of manipulation. Though they introduced an even easier bypass with that design…

      1. I’ve been making Cryptex(R) Security Boxes (www.cryptex.org) for 10 years now. I have a series of false tumblers in the rings so when you try this lock picking trick, you will feel a slight click… but there are 8 clicks on each ring and you don’t know which one is correct. You can narrow it down to 32,726 possible combinations still, but that is a lot to try one at a time until you get the correct one.

    1. It should be simple enough to make a shallow notch at each “digit” on the cryptex. Each notch would be slightly larger than the slack of any one tumbler, so just pulling on the thing gains you nothing (well, one combination that probably doesn’t work… you are back to brute force).

  4. I wonder if you could stagger the slots in the rings or maybe various height bolts and tiered rings, where you had to say, find one code, slide it out halfway, then have to guess a second code to pull it out further?

    1. Better still. Since it’s powered, have it issue small electric shocks if pulled when the code is wrong. Anyone without rubber gloves would soon give up a brute force attack.

      Still, nice build nonetheless.

  5. One possible way to stop it from being picked open is to add slight indentations to every key position in every ring so that pulling on the end with the wrong combination locks every ring in place. You can’t feel for the slot by rotating the rings because the rings won’t rotate.

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