multisignature

Multisignature, often abbreviated as multisig, is a cryptographic method that requires signatures from multiple independent keys to authorize a transaction or action. In a typical m-of-n multisignature scheme, a set of n public keys is associated with an account or contract, and at least m private keys must sign the message for it to be valid.

In practice, signatures can be produced by separate signers and then combined or submitted together to validate the transaction. Multisig can be implemented through threshold cryptography, where a cryptographic protocol guarantees that any valid combination of m partial signatures suffices, or through standard public-key multisignature arrangements where m distinct signatures are collected and verified independently.

Common uses include shared control of funds in wallets, corporate governance, escrow arrangements, and secure custody where no single party holds all keys. It mitigates single-point-of-compromise and improves resilience, but comes with coordination, recovery, and key-management challenges.

In blockchain systems, Bitcoin implements multisignature primarily via P2SH and P2WSH, enabling complex spending rules; Ethereum hosts multisig wallets as smart contracts (e.g., Gnosis Safe), which provide configurable M-of-N approvals. Other systems use threshold signatures, such as BLS or Schnorr-based schemes, to produce a single aggregated signature.

Security considerations include the risk of key loss or theft for any participating key, potential delays from cross-party coordination, secure backup needs, and design choices that affect privacy, transaction fees, and overall complexity. Improperly managed multisignature setups can lead to locked funds if too few keys remain or recovery options are not properly implemented.