Coordinated MPC: Transport Layer for Multi-Party Protocols

“Preview Talk” (by Team Dfns-Coord) @ TCPT2, in reply to the NIST Threshold Call

Abstract: This presentation dives into challenges of production deployment of Multi-Party Computation (MPC) protocols in production, specifically the message delivery layer that enables parties of the protocol to communicate. Its role is crucial: it has to fulfill strict security properties, with the security of the entire system at stake if they are not met. Implementing own delivery layer is error-prone, especially when other requirements are taken into account: such as operational simplicity, zero-downtime, and in-depth security. We will present the Coordinated MPC, the Transport Layer for MPC protocols that is designed and optimized for real-world MPC deployment and provides MPC-specific features, such as 1-round consensus on list of participants, globally unique execution nonce derivation, provable attribution of decryption. We will show the architecture of our Transport Layer which uses a central party (the coordinator) to relay messages. The coordinator is designed to be trustless, an adversary that fully controls it is limited to Denial-of-Service attacks only. Finally, we will discuss how the security of the protocol is proven in the Universally Composable (UC) model, allowing it to be safely composed with other UC protocols.

Joint work: Denis Varlakov, Antoine Urban, Nikita Sorokovikov

[Slides] Suggested readings:

• Preview Writeup (PDF): Coordinated MPC: Message delivery protocol designed for MPC systems with a central Coordinator