Multisig

Multisig, short for multi-signature, is a Bitcoin wallet arrangement that requires more than one key to authorize a spend. It is described as m-of-n: there are n keys total, and any m of them must sign before funds move. A 2-of-3, for example, has three keys and needs two to spend. This contrasts with a single-sig wallet, where one private key controls everything and that one key is a single point of failure for both loss and theft.

Why distribute the keys

In single-sig, whoever holds the key holds the coins, so one mistake, theft, fire, or coercion can mean total loss. Multisig spreads risk across keys you can store in different locations and on different devices. An attacker must now compromise multiple keys at once, and you can lose one key entirely without losing access, since the remaining keys still meet the threshold. The cost is added complexity in setup, backup, and recovery.

Collaborative custody

A popular pattern is collaborative custody, often a 2-of-3 where you hold two keys and a service holds the third recovery key. You remain the only party able to spend, since the provider's single key cannot reach the 2-of-3 threshold alone, so this is still genuine self-custody. The provider helps you recover if you lose one of your own keys, without ever being able to take your bitcoin.

Multisig policies are best captured as a Descriptor Wallet and signed across devices via Air-Gapped Signing.