Multisig (multi-signature)

A multisig (multi-signature) wallet is a wallet whose spending policy requires signatures from more than one private key. The most common configurations are 2-of-3 (any two of three keys must sign) and 3-of-5, but arbitrary M-of-N schemes are possible. The keys are typically held on separate devices, or by separate people, or in separate physical locations, so that no single compromise can move the funds.

The primary use cases are treasuries and businesses (no single employee can drain the wallet), high-value personal holdings (a lost or stolen single device does not lose the funds), and shared operations (a DAO or partnership requires coordinated action). Bitcoin multisig is implemented natively at the script level; Ethereum multisig uses smart contracts (Safe, formerly Gnosis Safe, is the dominant implementation).

The trade-off is complexity. Recovery scenarios must be planned in advance — what happens if one key holder is unreachable, what happens if a key is lost, whether the recovery threshold matches the operational threshold. Multisig is more secure than single-key when set up right, but a poorly planned multisig can be less recoverable than a single-key wallet.