Introduction

You’ve just received your Billfodl in the mail, and as you set it up you realize that each slot only holds 4 letters. “OH NO!” you think. “This Billfodl is broken! It doesn’t hold my entire seed phrase?

Don’t worry. There is nothing wrong with your Billfodl.

There is a very good reason the Billfodl only holds 4 letters of each word, and we will explain why below.

The BIP39 Word List

The Billfodl is a stainless steel device designed to store your recovery phrase.

The recovery phrase is made up of 12, 18, 0r 24 words from the BIP39 word list. This word list contains 2048 words.

For example, the keepkey hardware wallet only uses 12 words. The ledger series of wallets uses 24. Some software wallets sit in the middle with 18 backups words.

You may have noticed that some of these words are up to eight characters long. Why then does the Billfodl only let you backup four letters?

Because you only need the first four letters.Looking at the BIP39 word list will make it easier to understand.

Lets take a look at words #2016: winner and #2017: winter. They share the same first three letters ‘win’. But the fourth letter is different.

Now try to compare any other two words on the list. You will find that there are no two words with the same first four letters. All words are unique within the first four letters.

Many times, you will find that letters are unique within the first three letters. Some words, such as #1889: ugly are unique within only one letter.

What Will Happen if You Need to Recover a Crypto Wallet?

When you create a new wallet, you will choose the recover option - most wallets have this feature.

It will ask you to input your recovery phrase.

As you enter the first word, letter by letter, you will discover that the wallet will start autofilling the rest of the word for you. For instance, if your first word is “type”, you will input a “t” and an “y”. At this point, the wallet will likely show you “type” and “typical” and let you pick one.

You won’t have to keep choosing letters. The wallet is trying to make recovery easier for you.

Let’s take “ugly” as an example again. As soon as you input the letter “u”, it will probably force you to choose “ugly” since that is the only word that starts with a “u” in the BIP39 List.

Because of this feature of BIP39, backing up more than the first four letters is unnecessary.

Why Not Backup The Remaining Letters Anyway?

There are Four reasons we do not back up the remaing words.

Cost

Backing up more words than necessary means we would need to provide more tiles. We would also need to make the Billfodl bigger.

Doing this would require more labor and more raw materials. And the increased materials would make it heavier and cost more to ship. By not adding unnecessary labor and weight, we save you money.

Stability

Small contraptions like the Billfodl tend to hold up better in extreme elements, such as heat. We want the Billfodl to protect your recovery phrase in as many of these conditions as possible. The smaller we can make it the better.

Ease of Setup

More tiles means a longer set up process. The truth is, setting up a backup is not fun. Its tedious, no matter how you slice it. We’d prefer not to make you spend any more time on it than is necessary. Especially when there is no increased benefit to doing so.

Reproducibility

There is a small possibility that backing up more letters than you need is actually bad for the backup. We have tried to engineer the Billfodl so that the lock will not open unintentionally. We cannot always predict this though.

For example, if the Billfodl is in a house fire and a a heavy beam were to fall on it, the lock might break. When you go to pick it up, there is a chance the latch will come loose, and the tiles will fall out.

If this happens, you may be forced to collect the tiles and attempt to brute force the phrase using a computer. In this case, you want as little ‘noise’ in the signal as possible.

Having extra letters in your pile of tiles will only make this process more difficult. That is because it adds to the total number of different combinations possible.

Conclusion

If you have any other questions about why you only need four letters for a Billfodl or are curious about something else, send us an email to support@privacypros.io. We would be happy to help!