Losing access to a seed phrase can be a nightmare for cryptocurrency holders. Given the importance of seed phrases in self-custodial wallets, ensuring their safety and integrity is critical to safeguarding one’s digital assets. A seed phrase, also known as a recovery phrase, allows users to regain access to their wallets and prove ownership of their funds. However, what happens if a few words from the seed phrase are missing? Let’s explore how many missing words can be recovered and the risks involved.

Understanding Seed Phrases and Their Security Implications

Seed phrases typically consist of 12, 18, or 24 words and are considered “unhackable” due to the sheer computational power required to brute-force the entire sequence. These phrases are derived from a set list of 2,048 unique words, as established in the Bitcoin Improvement Proposal 39 (BIP-39). While the probability of brute-forcing an entire seed phrase is nearly impossible, recovering a few missing words is feasible within certain limits.

Industry experts suggest that it is possible to recover up to four missing words from a seed phrase. Beyond that, the required computational power increases exponentially, making the task impractical.

Seed Phrases vs. Private Keys: What’s the Difference?

A seed phrase is a mnemonic code composed of a sequence of words that can be used to restore a cryptocurrency wallet. In contrast, a private key is a string of 256 alphanumeric characters used to sign transactions and prove ownership of assets. While a private key is typically complex and difficult to memorize, a seed phrase is designed to be human-readable, making it easier to back up and recover.

Although seed phrases are easier to handle than private keys, they are still derived from the same underlying cryptographic data. Therefore, losing access to a seed phrase without a proper backup can lead to a loss of funds.

How Are Seed Phrases Structured?

The words in a seed phrase aren’t just randomly selected. They are derived from a specific list of 2,048 words outlined in BIP-39. When creating a wallet, the software generates a seed phrase using these words, ensuring that the phrase is unique and sufficiently complex.

The last word of a BIP-39 seed phrase is a checksum. This means it serves as a mathematical verification for the entire sequence. As a result, if you have the first 11 words of a 12-word phrase, you can calculate the final word using the checksum function, which simplifies the recovery process slightly.

Recovering Missing Words: What’s Possible?

According to Lucien Bourdon, an analyst at the hardware wallet firm Trezor, recovering a few missing words from a seed phrase is achievable using brute-force techniques. “If you are missing a few words, computers can try ‘brute force’ it, which means trying every possible guess,” says Bourdon. He also noted that the last word of a BIP-39 recovery phrase is a checksum, which can be calculated easily if you have the preceding words.

However, there are limits to what is recoverable. The time and computational energy required to guess missing words increase exponentially with each additional word. Here’s a rough estimate of the recoverability:

1. 1–2 missing words: Fairly recoverable with existing computational power.
2. 3–4 missing words: Recoverable but may require more time and resources.
3. Beyond 4 words: Computationally impractical and unlikely to succeed.

Tools and Techniques for Recovering Missing Words

For those who have lost a few words from their seed phrase, several tools can help. Software like BTCRecover, a popular open-source recovery tool on GitHub, can assist in recovering up to four missing words from a seed phrase. Some tech-savvy individuals have even reported success using AI tools like ChatGPT to assist in the recovery process, although these tools are less reliable and should be used with caution.

For instance, a user named “The Smart Ape” successfully recovered four missing words from his private key using a combination of BTCRecover and manual checks. However, attempting such recoveries without the right technical know-how can be risky and may lead to permanent loss of access.

Mitigating the Risk of Losing Seed Phrases

Given the critical role of seed phrases in cryptocurrency security, taking appropriate measures to safeguard them is essential. Here are some best practices:

• Create Multiple Backups: Always create multiple backups of your seed phrase and store them in separate, secure locations.
• Use Metal Backups: Consider using metal seed phrase backup solutions to protect against physical damage, such as fire or water.
• Double-Check for Accuracy: Verify that your seed phrase backup is complete and accurate. Even a single misplaced or missing word can render the backup useless.
• Never Share Your Seed Phrase: Your seed phrase should remain private. Sharing it with others or storing it digitally can expose your assets to risk.

Final Thoughts

While the technology exists to recover a few missing words from a seed phrase, this should not be relied upon as a safety net. The computational power and time required increase exponentially with each additional missing word, making it an impractical solution for those who lose more than four words. To ensure the safety of your digital assets, always keep a complete and accurate backup of your seed phrase.