Secure Multi-Party Computation

Cryptography letting several parties jointly compute a function over their private inputs so everyone learns the correct result but no one learns anyone else's input — removing the need for a trusted third party who would see all the data. In crypto it underpins MPC wallets and threshold signing (a key is never assembled in one place). Its guarantees depend on the adversary model (semi-honest vs malicious) and how many parties may collude, and its privacy costs communication/compute.