# Multi-party computation (MPC)

Multi-party computation (MPC) is a cryptographic technique that splits a private key into shares held by different parties, who jointly produce a signature without any of them ever holding the complete key. In custody, MPC distributes approval power; it does not by itself decide who controls the key material.

## What MPC does and does not solve in custody

MPC removes single points of compromise at signing time and enables flexible approval policies. It does not change the signature scheme the blockchain accepts, cannot be air-gapped by design when a co-signing service must stay connected, and hash-based post-quantum signature schemes are mathematically incompatible with it.

Taurus offers MPC algorithms on top of an HSM root of trust, so banks get distributed approval without giving up full private key sovereignty or post-quantum options. Taurus custody has no dependency on MPC.

FAQ:

- Is MPC custody post-quantum ready? Not today. Threshold protocols for the new NIST lattice signatures are recent and not production-validated, and hash-based schemes are mathematically incompatible with MPC because hash functions lack the algebraic structure MPC needs. HSM-based custody supports every post-quantum signature family now.

Related: https://www.taurushq.com/glossary/hardware-security-module-hsm/ https://www.taurushq.com/security/post-quantum-ready/ https://www.taurushq.com/glossary/hash-based-signatures/

Learn more: https://www.taurushq.com/glossary/multi-party-computation-mpc/