Secure Multi-Party Computation (MPC)

Computing on Secrets Nobody Reveals

Secure multi-party computation (MPC) is a branch of cryptography that lets several parties jointly compute a function over their individual private inputs, so that everyone learns the correct result but no one learns anyone else's input. The classic illustration is the 'millionaires' problem': two people want to find out who is richer without either revealing how much money they have. MPC makes this possible — they can compute 'who has more' while each keeps their actual number secret. Generalised, MPC allows a group to compute any agreed result from data they each want to keep private, replacing the usual need for a trusted third party who would otherwise have to see everyone's data to do the calculation.

Why It's Powerful

The power of MPC is that it removes the trusted middleman. Normally, to compute something over multiple parties' private data (a shared average, a matching, a joint decision), someone has to collect everyone's raw data — creating a honeypot and a party who must be trusted. MPC lets the computation happen collaboratively with the data staying split and hidden, so there is no single point that ever sees the secrets. In crypto specifically, this underlies MPC wallets (where a private key is never assembled in one place — several parties jointly produce signatures without any one holding the whole key) and a range of privacy-preserving and threshold systems. It is a way to get the benefit of cooperation on sensitive data without the risk of centralising that data.

• MPC lets parties jointly compute a result over private inputs, revealing only the output
• The 'millionaires' problem': learn who is richer without revealing amounts
• It removes the need for a trusted third party who would see everyone's data
• In crypto it underpins MPC wallets and threshold signing (no single key holder)