Do It the Right Way — Protecting Your Paper Backups

Thieves Are Smart, but You Are Smarter

Assuming you have printed out your mnemonic phrases, private keys, or passwords using a split method, you are ready to put them away in secured places. You will place them in the envelope, write down some notes, and voilà. As much as this sounds like a good idea, let us look at some problems that are not immediately obvious.

If one of your pieces was compromised, you might not even notice. Anyone who wants to steal your confidential data will likely try to conceal any traces of a crime. If you do not find that one of your envelopes was opened early enough, you increase the chance of leaking your information completely.

Printouts

The goal is to wrap the printouts in a way that makes it very obvious they were compromised. The package should have unique traits and should not be possible to replace with a recreated copy, should not be possible to view the content without opening it, and should not be possible to open with steam and re-seal it.

Marking

Good marking techniques need to consider protecting against the possibility of recreating the envelope. In the end, an intruder will not care how well your package was protected if they can replace it with a perfectly recreated copy. Noticing unintended interference is critically important, and probably the most effective way of marking is using self-invented techniques.

One way we would suggest is randomly placing the envelopes on top of one another and marking them with one stroke using a marker. Make sure that each envelope contains part of the ornament. You can even take a photo to act as a reference to examine if in doubt. Of course, do not share these photos with anyone you do not trust.

Opaque Wrap

There is also a chance that wrongly protected content could be looked through the envelope. Using a very strong torch and capturing the image can potentially leak the information without leaving any traces behind. Placing a printout in a black protective sleeve before sealing in the envelope would very likely fix the problem — ideally the kind that requires protection against light, such as those used for photographic paper.

Before distributing the envelopes, it is strongly recommended to do a small experiment. Place your printout in the protective sleeve, slide it into the envelope, take a torch, and try to look through. You can take a step further and capture the image. Using photo editing tools, try to recreate the content. If you cannot, your content is likely to be well protected.

Sealing

Sealing the package can be quite tricky. You cannot prevent anyone from opening it, but you can seal it in a way that makes it obvious it was opened by an unintended person. Choosing the correct envelopes for the job is very critical. Standard sealing may not be enough, and you will need to apply your own solution. Using strong double-sided tape can do the trick — trying to open the envelopes will rip them apart.

Environment Impact

Let us not focus only on intruders. There could be other natural factors that can cause your information to be damaged. In the end, your job is to minimise the risk of losing data one way or the other.

The printouts should always be kept in conditions that are friendly for long-term storage:

• They should not be exposed to the sun. Sunlight can bleach out the printouts.
• They should be kept in a dry environment. Moisture can completely damage printouts and make them unreadable.
• Black protective plastic sleeves mentioned earlier can help. When the paper sits in the sleeve, ensure it is vacuumed as much as possible — air can condensate into droplets of water and impact the prints.

Locations

Your documents should be hidden in secured locations. At the same time, they should be easy to access for you and anyone you need to share with, but hard to access by anyone else. In the end, your protection is only as good as how quickly you can counter the potential loss.

One of the biggest challenges you will face is finding locations where you can store your printouts. Three locations are optimal because most likely the average person will not be able to find more. A system that requires more places creates the potential problem of poor security. Your hidden spots should be an optimal balance of easy to reach by yourself and hard to find by anyone else.