Secure Multi Party Computation

 A considerable discussion of the problem in the most recent issue of the ACM.  In general the notion of Multi Party Computation (MPC) was something I had not thought about directly,  but since my background is about computation, this is worth thinking through.

Secure Multiparty Computation   By Yehuda Lindell

This article also contains a video at :  bit.ly/3nD1DDm

Communications of the ACM, January 2021, Vol. 64 No. 1, Pages 86-96   10.1145/3387108

Distributed computing considers the scenario where a number of distinct, yet connected, computing devices (or parties) wish to carry out a joint computation of some function. For example, these devices may be servers that hold a distributed database system, and the function to be computed may be a database update of some kind. The aim of secure multiparty computation is to enable parties to carry out such distributed computing tasks in a secure manner. 

Whereas distributed computing often deals with questions of computing under the threat of machine crashes and other inadvertent faults, secure multiparty computation is concerned with the possibility of deliberately malicious behavior by some adversarial entity (these have also been considered in the distributed literature where they are called Byzantine faults). That is, it is assumed that a protocol execution may come under "attack" by an external entity, or even by a subset of the participating parties. 

The aim of this attack may be to learn private information or cause the result of the computation to be incorrect. Thus, two important requirements on any secure computation protocols are privacy and correctness. The privacy requirement states that nothing should be learned beyond what is absolutely necessary; more exactly, parties should learn their output and nothing else. The correctness requirement states that each party should receive its correct output. Therefore, the adversary must not be able to cause the result of the computation to deviate from the function that the parties had set out to compute. ...