” In cryptography, secure multiparty computation is a problem that was initially suggested by Andrew C. Yao in a 1982 paper. In that publication, the millionaire problem was introduced: Alice and Bob are two millionaires who want to find out which is richer without revealing the precise amount of their wealth. Yao proposed a solution allowing Alice and Bob to satisfy their curiosity while respecting the constraints.

This problem and result gave way to a generalization called multiparty computation (MPC) protocols. In a MPC, we have a given number of participants p1, p2, …, pN, each having a private data, respectively d1, d2, …, dN. The participants want to compute the value of a public function F on N variables at the point (d1, d2, …, dN). A MPC protocol is dubbed secure if no participant can learn more from the description of the public function and the result of the global calculation than what he/she can learn from his/her own entry - under particular conditions depending on the model used. ”

http://www.cs.ut.ee/~lipmaa/crypto/link/mpc/