MPC (Multi-Party Computation)

Definition

MPC (Multi-Party Computation) is a cryptographic technique that allows a Bitcoin transaction to be signed without the full private key ever existing in a single place. Instead of a single key, the key is split into several fragments (shares) held by different parties; to sign, those parties run a joint protocol that produces a valid signature without ever reconstructing the entire key. If an attacker compromises a single fragment, they have nothing with which to move funds.

MPC is often compared to multisig, because both eliminate the single point of failure, but they operate on different planes. Multisig is native to Bitcoin: the blockchain itself records that, for example, 2 of 3 signatures are required. MPC, by contrast, happens off-chain: to the network it is a single standard signature, which makes it more flexible (it works the same on any blockchain), more private (it does not expose the signing policy on-chain) and easier to integrate into operational workflows, at the cost of relying on the provider's implementation rather than the protocol itself.

In practice, MPC has become the foundation of much of institutional custody. Providers such as Fireblocks and BitGo use it — alone or combined with multisig schemes and cold storage — so that no employee or server concentrates the ability to sign, distributing the shares across devices, data centers and, sometimes, the client themselves. It is a key piece of how corporate treasuries and ETFs protect large Bitcoin reserves.

In Context