What is MPC?

Multi-party computation (MPC) is a core cryptographic primitive that has been studied since the early 1980s, but has seen little use in DeFi before Renegade.

To best understand MPC, it is easiest to compare to the "ideal functionality" that MPC implements. In this setting, multiple parties send some private data to a trusted evaluator. Once the evaluator receives all the private data, it computes a function on that data and then sends the function output to all the parties.

Note that the important property here is that the trusted evaluator only sends the output to each party, and is trusted to forget all the private inputs. This allows for computation of a function without needing to reveal the inputs to everyone.

For example, two parties could each hold two private numbers and compute a comparator between the two private values, outputting a single bit to determine who has the larger input.

The core idea of a MPC protocol is that it lets you implement the above functionality without needing to trust a central party. That is, MPC allows for multiple mutually-distrusting parties to compute a function output on secret input data.