BIP85: Control all other seed phrases with one seed

Imagine you have a master key, the "master seed," that not only gives you a single wallet, but functions like a kind of tree. From this master key (or trunk), you can derive many branches, called "child seeds," each of which represents its own wallet. The great thing about this is that you only need to back up the master seed, and you can access all your derived wallets at any time.

How does the derivation of child seeds work?

The process behind BIP85 is similar to the idea of a key system, where you have a master key. This master key can generate multiple "subkeys," but conversely, these subkeys cannot trace the master key.

Imagine your master seed is like a large lock. With this lock, you can create as many keys as you like—each wallet you open with it will function completely independently and securely, as if it were a completely independent wallet. But the difference is: instead of storing each individual key, you only need to secure the lock. Your master seed is this "lock," and the derived wallets are the child seeds.

What happens in detail?

BIP85 uses your master seed and a so-called "index" (a number) to continually generate new, independent seeds (child seeds). Each index generates its own child seed, and each of these child seeds can be used for its own wallet. This means that with your master seed, you can create an infinite number of child seeds, each with its own wallet and Bitcoin address.

An example:

• Master Seed + Index 0 = Wallet A
• Master Seed + Index 1 = Wallet B
• Master Seed + Index 2 = Wallet C

Wallets A, B, and C have nothing to do with each other, except that they all originate from the same master seed. Each of these child seeds functions like a regular seed—you can use it to create a wallet and receive and send Bitcoins. They are just as secure as any other seed.

Important safety points

• Randomness of the master seed: It's crucial that your master seed is truly randomly and securely generated. This is the only way to ensure no one can guess it. It's also extremely important to store this master seed securely, preferably offline or stamped on metal, so it's not lost through fire, water, or physical destruction.
• Backup only from the master seed: The big advantage here: You only have to a Store your seed securely – the master seed. If you protect this seed well, you'll protect all derived wallets, including hot wallets and even your Phoenix wallet. This saves you the hassle of backing up dozens of different seeds and simultaneously increases the security of all your wallets.
• Do not recommend using passphrases: While you can add a passphrase to generate even more complex child seeds, this quickly becomes complicated and increases the risk of errors. Therefore, in most cases, it's better to work with just the master seed.

Use cases of BIP85

1. Simplified wallet management: You can derive all wallets from a single master seed, whether for your personal wallets or for different projects. You only need to secure this one master seed, and all other wallets will be securely derived from it.
2. Nostr and Bitcoin: With BIP85, you can not only derive Bitcoin wallets, but also the "Nostr NPub," which serves as your public key for the decentralized Nostr network. This means you have a secure, recoverable method for operating outside of the Bitcoin network.
3. Wallets for family membersImagine you derive the seed for your son's wallet from your master seed. If your son makes a major mistake and loses access to his wallet, you, as his father, can restore it because the seed comes from your master seed. This increases security in case someone is inexperienced or makes a serious mistake.
4. Different wallets for different purposes: You can create different wallets for different purposes—one for daily use (e.g., hot wallet), one for long-term savings (cold storage), and one for special projects. All of these wallets can be derived from your master seed, and you retain full control over their security through a single backup.

Here's how you can use the Specter DIY BIP85:

In the dashboard (after entering the seed phrase) click Deterministic derivation (BIP-85) press.

Then you can MNEMONICS the desired seed phrase. I recommend 12 seed words, as more than that offers no security advantage. And 12 are easier to type. So 12-word mnemonic.

Now you can choose a derivation index you want to use. The same seed phrase is always derived from the same number. This number should be noted down so that it can be easily derived in an emergency. The choice of number is irrelevant here, but it is recommended to 0 to start, which is already preset anyway.

After confirming with the check mark in the bottom right corner, the child seed can be copied. Use now (load to device), is used as a seed phrase, where you will then be taken to the new seed phrase dashboard. The previous master seed will then be discarded and would need to be re-entered if necessary.

Conclusion

BIP85 brings enormous benefits to Bitcoin users, as it not only simplifies wallet management and backup, but also increases security. Instead of backing up multiple seeds for different wallets, it is sufficient to simply to punch a seed phrase into steel and thus ensure the security of all your wallets. You can derive as many child seeds as you like—whether for your own purposes, Nostr, or for family members—and have control over how many wallets you create and manage.

The important thing remains: Your master seed is the heart of your wallet. Keep it safe, and you'll have a firm grip on all your other wallets.