This article explains what recovery words are and why they are the master key to your cryptocurrency.

What are recovery words?

When you set up a cryptocurrency wallet, it generates a master seed, which is a single secret that all your keys are calculated from. These words serve as the backup of your wallet's master seed. If your BitBox02 is ever lost, stolen, or damaged, you can use these words to restore full access to your funds on a new device.

How recovery words work (BIP39 standard)

From a secret number to words

Your wallet's master seed is a very long, secret random number. To make this secret easier for a human to write down and back up, the number is encoded into a list of English recovery words.

The BIP39 word list

The BitBox02 uses the industry standard called BIP39. This standard uses a specific, well-known list of 2048 English words. You can view the official word list here.

• The first four letters of each word are unique, which helps identify it correctly, though writing the full word is recommended for better readability.
• The system includes an integrated consistency check that helps detect mistakes during the setup or restoration process.

Security level (entropy)

The number of words in your phrase relates directly to its security level. More words create a combination that is exponentially harder to guess:

• 12 words: 128 bits of security (2^128 combinations)
• 18 words: 192 bits of security (2^192 combinations)
• 24 words: 256 bits of security (2^256 combinations)

For more technical details, you can read the official BIP39 specification on GitHub.

Why a written backup is important

The BitBox02 automatically creates a backup of your wallet on the included microSD card during setup. While this is convenient, we highly recommend creating an additional, physical backup by writing down your 24 recovery words.

This handwritten copy provides an additional layer of security. It ensures you can access your crypto, even if something happens to both your BitBox02 and your microSD card.

Critical security rules for your words

Your recovery words are the keys to your entire crypto wallet. Anyone who has access to them can control and steal your funds.  You must treat them with extreme care by following these rules:

• Keep them offline, always. Never store your recovery words in any digital format. This includes taking photos, using a password manager, or saving them in a text file, email, or cloud storage.
• Work in private. When you view or write down your words, make sure you are in a secure location where no person or camera can see them.
• Never type them on a computer. Only enter your recovery words directly on your BitBox02.  Your computer could have hidden malware that steals your words.
• Do not make photocopies. Modern printers and copiers often store a digital copy of what they scan.

How to store your recovery words

Once you have written down your recovery words, store the physical copy in a secure, private, and durable location. Good options include a locked drawer, a home safe, or a bank deposit box.

For improved durability against fire or water damage, consider these options:

• Backup card: A simple, laminated card for writing down your words.
• Steelwallet: A robust, stainless steel device for punching in your words, protecting them from physical damage.

Advanced: The optional passphrase

For an even higher level of security, the BitBox02 supports an optional passphrase, sometimes called a "25th word". This feature allows you to create separate, hidden wallets that require both your 24 recovery words AND a unique passphrase to access. To learn more about this advanced feature, please see our guides on the benefits and risks of passphrases.