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BIP-85 | Make Child Keys From One Master Seed
Learn What BIP85 Is and How You Can Use It for Key Management
Manage all your wallets and accounts with 1 device
- Make up to 10.000 child keys from one master seed
- Hot wallets, Lightning wallets, mix wallets and even Nostr
- Compromised child keys won't endanger the master seed!
- Help family and friends (who trust you) on their Bitcoin journey
- Learn whether you should use BIP85 for multisignature
What is BIP85?
BIP85 or BIP-85, which is short for Bitcoin Improvement Protocol 85 is a standard that allows you to create up to 10.000 child keys from a single master seed (?). You can use these child keys between different wallets, formats and even protocols.
Derivation between the master seed and the child keys is one way. This means that you can easily derive the chid key from the seed, but you can’t derive the seed from a child key. This means that if a child key is compromised, you can just create a new one from the seed. Your master seed and all the other child keys will still be secure.
This means that protecting your master seed is extra important. If your master seed get compromised, all your child keys are compromised too. It’s recommended to create your master seed always on a BIP85 compatible hardware wallet and store the seed in a safe location. It’s the only easy way to be sure that your seed will never be exposed online.
BIP85 is a perfect tool to manage keys between different wallets in a secure and convenient way.
How Does BIP85 Work?
BIP85 is a protocol build on BIP32 and BIP39 to enable the creation of child keys from a master seed. The protocol uses derivation paths (?) to index the BIP85 child keys. This ensures that you will always get the same child key if you follow the derivation path from the seed.
The derivation path can point to another format or protocol, which makes it possible to manage keys for different software. You can think of hot wallets, Lightning wallets and even Nostr accounts.
Why Use Child Keys
But why would you use BIP85 child keys? It makes it much easier to manage your own keys and you can manage wallets for other people who trust you. If you have different Bitcoin wallets for different use cases, it’s not convenient to secure a seed for every single wallet.
If you are very confident that you have a really secure location to store your seed, BIP85 enables you to store just one master seed and make a child key for all your wallets. Now you just have one backup that you have to protect with all your focus, instead of multiple seeds with all different security requirements.
You can also use BIP85 to help a friend or family member who really trust you with backing up their Bitcoin wallet. They might not have the money for a hardware wallet or the knowledge or confidence to properly backup their wallet themselves.
You can create a child key for them from your military level secured master seed, so they don’t have to backup anything. If something happens to their wallet, you can just recover the key for them. Note that trust is extremely important, since you will be able to control their Bitcoin!
BIP85 and Multisignature
For a general multisig setup, we do not recommend that you use BIP-85 to generate your keys. The reason is that this will make your master seed a single point of failure, which defeats the purpose of the multisig. Every key in a multisig should have it’s own seed and safe storage location.
However, you can use one of the seeds of your multisig to create child keys for other wallets and accounts. For example: You can use the seed of one signer that you store in a locker at home as a master seed for your spending wallet, your Lightning wallet, your Nostr account and your mother’s wallet.
In this case it’s a good idea to choose a hardware wallet that is both BIP85 compatible and very secure against physical attacks, like a Coldcard. For your other signers you can select for different features.
Signing Devices that Support BIP85
Not all hardware wallets are compatible with BIP85, so if you want to make child keys you have to choose the right device. Below the signing devices that support BIP85 and the most important other features they come with:
Coldcard Q1
Are you looking for a hardware wallet with the latest security features like QR air-gapped signing, trick me pin, roll ’n dice and can be used as a password manager and protects extremely good against physical attacks and supports BIP85, the Coldcard Q1 is the perfect device! It’s the newest hardware device by Coinkite and the most feature rich device on the market. This device is perfect to manage all your security from one single place. If you pay with Bitcoin and use the code CKBTC, you get 5% off!
Coldcard MK4
Do you want a device that is highly regarded in the Bitcoin community, super feature rich, cheaper and with a longer track record than the Q1, super secure against physical attacks and compatible with BIP85, then the Coldcard MK4 is the signer you need. It’s the perfect device to use at home as described earlier on this page! If you pay with Bitcoin and use the code CKBTC, you get 5% off!
Passport
Do you want a user friendly hardware wallet that supports among others air-gapped signing with QR and BIP85? Get a Passport device! It is fully open source and if you are not comfortable to setup the device yourself, you can get 1 hour onboarding service through their concierge program. If you use the code MULTISIGSIGNER, you get $10,- off!
Blockstream Jade
Do you want the cheapest hardware wallet to make child keys? The Blockstream jade is the cheapest hardware wallet with BIP85 support. Don’t let the price mislead you: It’s a very good hardware wallet that comes with QR air-gapped signing and a virtual secure element. Also, if you use Liquid to make cheap transactions, the blockstream jade is the perfect device for you! If you use the code MULTISIGSIGNER, you get 10% off!
