TM 42-10

Warranty Void if Seal Is Broken

Experiences at Defcon 22: Tamper Evident Contest

I have years of experience breaking tamper evident seals; this should be easy! Except… that is not the point. The goal of the contest was removing and replacing the tamper evident seals, without damaging them. This sounded fun, so thetic and I became team Golden Goblin.

Our final tally: 10 stickers, 18” of tape, and 5 clasps removed and replaced. One seal melted beyond recognition (my fault). One clasp not removed (I was doing it wrong).

The following is a collection of techniques for removing and replacing each seal. Some of the best techniques I know are not mine. I will try to keep this clear moving forward. Also a huge thank you to the winning team, Imparted Event, whose excellent documentation is available through the contest results page in the Defcon Forums.

Tamper Evident Tape:

I applied acetone to the edge of the tape, and peeled it back slowly as the glue softened. This works best if the box is oriented in such a way as to peel the tape down, so that gravity pulls the excess acetone down into the point where the tape is still sticking. I believe I could have scored perfectly on the tape with a little more care. Wearing nitrile gloves at this point, I noticed that the tamper evident tape did not stick to the gloves. I layed out clean gloves on the table, and stuck the tape to them for safekeeping. I spent some extra energy and messed up the tape trying to use acetone to remove tape from tape. Common sense soon prevailed, and I realized that tape comes on a roll. In order to apply the tape, it has to be easily removable from itself, and marring it with acetone was not helping, as the tape seals tightly to the layer of tape under it.

Tamper evident stickers:

One was just a small piece of red tamper evident tape, which I used acetone to remove. Pleased with my relative success there, I tried to use acetone on the next sticker I encountered. Unfortunately… acetone sometimes is not the correct answer. One horribly melted sticker later, I switched to using heat.

Lacking fancy heating tools, thetic used the hair dryer in the hotel room to heat the stickers. After some trial and error, we were able to remove stickers without significant damage. It should be noted here that the tool used makes a difference! I started using a round 2-sided rake from my lockpick set to lift the stickers. We soon learned that hot glue is soft, and found this was leaving marks when we put them back. I transitioned to using the edge of a knife to start, and then my gloved hand to lift the stickers. This worked quite well, and with some patience, I believe we could acheive perfect scores on the seals used this time. I have heard rumors of seals that discoler when heated, I am researching this in order to be prepared for next year.

The physical clasps did not go well.

PG & E Clear Padlock seal:

After much debate, we determined the best course of action was to remove the wire from a spare padlock seal, and replace the wire in this one. Research and the book of techniques from Tamper Evident Village lead us to think that electrolysis was a viable solution. After much frustration, we abandoned this approach (which may be valid, if done correctly) and I shimmed each side with the needle I was using for acetone. My clumsiness here caused scratches on the inside of the padlock seal, which were visible on close inspection. I later learned that Imparted Event used an 18G piercing needle, and shimmed it much more cleanly. Comparing methods based on their documentation, I believe the ideal approach would be to use 2 18G x 2.5” needles, and shim both sides of the padlock seal at the same time. This would prevent damage to the wire.

Metal ball seal:

I determined from destruction of a spare that this locks using two metal rings. Using a hook from my lockpick set, I was able to pull the rings out of their locking holes. However, in doing so I let them fall into a different hole, preventing the seal from locking again. After some trial and error, with the clock running down on Saturday, I cut the metal end of the seal and fashioned a crude catch. This almost worked, in that it passed the first tug test. When the second judge examined it, however, it fell apart in his hands. I believe it is possible to use tools to move the rings out of place enough to open the clasp, without completely destroying it as I did. Imparted Event removed half of the ball, moved the rings with plyers, and put it together again with a piece from a spare seal. This is clearly the easier approach, however I will continue to attempt my approach until I understand whether it can work.

Easy lock seal:

This is fairly easy to shim. Unfortunately, we spent some time learning how to shim it, and I scuffed the seal in my attempts. We did succeed, using two shims made from a can of Guiness. One shim goes on either side, in order to move all the locking pieces.

Zip seal:

Ok, this was really easy. It is as easy as shimming a ziptie, or handcuffs, or whatever. The only difference is it latches on both sides, so it takes 2 shims at once.

Plunger seal:

In this case I completely failed. Not only did I horribly mar the plastic, I failed to open it. I attempted shimming, many times, and failed. We learned, reading the write-up from Imparted Event, that we should have removed the plug from it, opened it, and then replaced and resealed the plug.

Uline cable seal: This is a 1/16” twisted steel cable, held in place by a cam. My approach was very slow, however it earned a perfect score (most of the teams did). I used plyers to grip the cable, and slowly twisted it. As the cable is not smooth, this causes the cam to bounce. Each bounce of the cam allowed me to remove a tiny amount of cable. Finnesse is required, and patience. Imparted Event used a shim, and as I imagine it took only seconds to do, that is likely the better approach.

Overall, this was an incredibly fun contest. I hope we do better next year, and I am determined to never break a warranty sticker again. I might remove it and put it on the boss’s desk though…


Yet another feature that I never needed before:

Send message to another user:

  write <user> [terminal]

The other user sees the message, but his terminal is still looking for commands. The cure for this is to use write (by itself, it assumes you are talking to the other user) to initiate a reply.

After that, it is just like any other chat, until each user presses ctrl-d.