Why do you only need the first 4 letters of a BIP39 seed phrase?

Hardware wallets are an essential tool for anyone looking to invest in digital assets. These wallets store your private keys, which are used to access your crypto on the blockchain. You can think of it as a password. However, losing your private keys can mean losing access to your funds forever. A private key is a long string of characters that is difficult to store, enter or remember. This is where seed phrases come in handy.

What is a seed phrase?

A seed phrase, also called a recovery phrase or mnemonic, is a series of words used to generate your private keys. These words are generated with a specific algorithm that ensures they are unique and random. This is all done according to the Bitcoin Improvement Proposal 39 (BIP-39). The seed phrase usually consists of 12, 18 or 24 words, and it is essential to keep it secure and well preserved.

Because these words come from an official, open-source, and industry-standard word list with only 2048 words, it becomes clear why you only need the first 4 letters of a seed phrase. In fact, each word is unique after the first 4 letters. We discuss this in more detail later.

The seed phrase should always be kept in the correct order. Do not change words or delete them for “security purposes” thinking you will remember it. History has shown that remembering and splitting seed phrases are the biggest causes of losing access to cryptocurrencies.

To give an example, a seed phrase can look like this. The example may even contain some words that are also in your seed phrase. But don’t worry, there are countless different seed phrase possibilities.

hotel obvious agent lecture gadget evil jealous keen fragile before damp clarify

You may have seen some of your seed words online somewhere before. Of course, this was not your actual seed phrase, but the words are from an open-source and industry-standard word list. In the official BIP-39 word list, there are 2048 words. This list can be found on various websites, in physical copies and many other places online.

The official documentation of the BIP-39 protocol, from which the seed phrases originate, states the following about the vocabulary:

“An ideal glossary has the following characteristics:

(a) Smart selection of words

• The word list is constructed so that it is sufficient to type the first four letters to unambiguously identify the word.

(b) Avoid similar words

• Word pairs such as “build” and “built,” “woman” and “women,” or “quick” and “quickly” not only make remembering the sentence more difficult, but are also more error-prone and harder to guess.

(c) Sorted glossary

• The word list is sorted, which allows more efficient codeword lookup (e.g., implementations can use a binary search instead of a linear search).
• This also allows the use of a trie (a prefix tree), for example, for better compression.”

How does a seed phrase work?

When you create a new wallet, you will be asked to write down your seed phrase. This phrase is used to generate your private keys, which are then used to access your funds. If you lose your private keys, you can restore your wallet using your seed phrase.

Seed phrases work through a specific algorithm that generates a unique set of private keys. This algorithm uses a combination of your seed phrase and a random number generator to create your private keys. This means that your seed phrase is all you need to recover your wallet.

How do you restore your wallet with a seed phrase?

If you lose your private keys, you can recover your wallet using your seed phrase. To do this, you must enter your seed phrase into a wallet that supports seed phrase recovery. The wallet will then use the algorithm to generate your private keys and give you access to your funds.

1. Find your seed phrase. It may be stored on paper, digitally or preferably on a seed phrase backup.
2. Reset your wallet to restore it.
3. Start by entering the words in the correct order. Your wallet will automatically complete the words or give suggestions in most cases. Remember, after the first 4 letters, each seed phrase word is unique.
4. Once all the words are entered, your wallet will confirm the seed words and give you access, or indicate that the seed phrase is incorrect.

Why do I only need the first 4 letters of a seed phrase?

Seed phrases consist of a list of words, and each word is unique. However, you do not have to enter the entire word to restore your wallet. You only need to enter or save the first four letters of each word. These are the actual first four letters, not just the unique first four letters.

This is because the first four letters of each word are unique enough to identify the entire word. For example, if your seed phrase contains the word “elephant,” you only need to enter “elep” to recover your wallet. This makes restoring a seed phrase much easier and faster.

The BIP-39 protocol and the words in the glossary are carefully chosen as common words that are unique after the first four letters. Just look at this example:

Since all words are unique after the third letter, and your wallet knows the word list, it can automatically complete the words or make suggestions.

Conclusion

Seed phrases are an essential tool for anyone looking to invest in cryptocurrencies. They provide an extra layer of security and ensure that you can always recover your wallet, even if you lose your private keys. Remember, it is crucial to keep your seed phrase safe and well stored.