Applying Basic Math to Slightly Secure Your Written Backups

If you hold some bitcoin or cryptocurrencies, you probably already know that storing your funds using a reputable non-custodial wallet is absolutely necessary for increased privacy and security; and that includes keeping your wallet’s recovery seed words offline on pieces of paper.

One of the hurdles of this though, is keeping your seed paper secure and out of reach of peering eyes. Are you using a secure and reputable wallet like a Ledger hardware wallet? The wallet’s security is almost pointless if your written backup is not secure in the first place.

Besides keeping your seed papers on a heavy-duty and bolted-down safe, one decent solution would be to apply a bit of very basic elementary mathematics that pretty much anyone can do.

Advantages

If you simply write down your wallet’s 12-24 word seed on a piece of paper, and keep it somewhere easily accessible like a drawer, or a small, lightweight, non-bolted down safe(that could be easily carried and stolen); someone could potentially gain control over your funds if that certain person somehow manages to gain access to your seed paper.

However, if someone gained access to your seed paper whereas you applied this basic mathematics on, they still wouldn’t be able to access your funds if they don’t know your ‘secret number’ that you’ve used to somewhat ‘hide’ the word seed.

The Method

With most if not all bitcoin and cryptocurrency wallets, they use the english word list of the bip-0039 standard, which consists of 2048 words in total.

If we take a look at the english.txt file on bitcoin’s bip-0039 repository on GitHub or if you download and open the english.txt file on a text editor, each single word has a corresponding number derived from it’s alphabetical order:

For instance, we have a wallet with a 12-word recovery seed that consists of these words:

depart wood pink other abstract blouse bunker boss anxiety town cruel gift

Based on the alphabetical word ordering from the bip-0039 english.txt file, the number equivalent of these words are as follows(counting starts from 1, not 0):

depart - 471
wood - 2026
pink - 1321
other - 1257
abstract - 8
blouse - 194
bunker - 244
boss - 210
anxiety - 81
town - 1843
cruel - 421
gift - 783

Instead of writing these numbers down on a piece of paper, we apply basic mathematics to somewhat hide your seed backup.

Now, think of a number. Preferably, a number that consists of 4 or more digits, and could be easily remembered by you.

For this example and for simplicity sake, we’re going to use the number 5555. We’re now going to use this number and add it to your recovery seed numbers, as such:

depart - 471 + 5555 = 6026
wood - 2026 + 5555 = 7581
pink - 1321 + 5555 = 6876
other - 1257 + 5555 = 6812
abstract - 8 + 5555 = 5563
blouse - 194 + 5555 = 5749
bunker - 244 + 5555 = 5799
boss - 210 + 5555 = 5765
anxiety - 81 + 5555 = 5636
town - 1843 + 5555 = 7398
cruel - 421 + 5555 = 5976
gift - 783 + 5555 = 6338

Now that we’ve applied some basic elementary mathematics to the number equivalent of each word, we can now write down the ‘hidden’ numbers on a piece of paper.

If we’re going to recover our wallet to a different device or a different app in the future, we simply ‘decrypt’ the written numbers by simply subtracting our ‘secret number‘(5555) to the written numbers. We then take the difference from the subtracted numbers and look for their word equivalent on the bip-0039 english word list.

You can now use these words to recover your wallet.

Final Thoughts

While using this method could make it slightly more difficult for a hacker to access your funds, we still suggest against storing the backup digitally and online; just to be extra sure. Remember, this is only a very thin layer of security to your recovery seed backup. If someone gains access to your recovery seed, transfer the funds to a newly generated wallet immediately. Using this method only slightly delays the thief of accessing your funds if he/she somehow gains hold of your seed paper, as they could use brute-force methods to find your original 12-24 word seed.

Also, take note that we just used the number 5555 just for simplicity sake. In a real world scenario, a number that’s more than 4 random digits(e.g. 8242, 6382, etc) is a lot better in terms of security, and to remove hints that the numbers aren’t a backup of a bitcoin or cryptocurrency wallet.

Finally, instead of using your computer’s or your smartphone’s calculator app, we suggest using your old shelf calculator, school scientific calculator, or your old touchpad mobile phone’s calculator instead. Just to be extra sure, as a malware on your computer or your smartphone might be recording your keystrokes.