What Is a Multisignature (Multisig) Scheme and How Does It Extend ECDSA?

A multisignature scheme requires multiple private keys to sign a transaction before it is considered valid, for example, 2-of-3 keys. This extends ECDSA by requiring a set of distinct, valid ECDSA signatures to authorize a single spend.

It is used for enhanced security, corporate treasury management, and escrow services. It mitigates the risk of a single point of failure by distributing control over the funds.