MPC Protocol
For a comprehensive technical analysis and formal security proofs, see the Hashi MPC Whitepaper.
What MPC protocols does Hashi use?
Sui validators use several Multi-Party Computation (MPC) protocols to implement a threshold Schnorr signer: Distributed Key Generation (DKG) for generating a key, key rotation for redistributing the key on committee changes, and a distributed signing protocol for signing transactions. The Mysten Labs cryptography team based the protocols on prior published work and modified and improved them.
What are the liveness and security parameters for Hashi MPC?
Two values, f and t, parametrize these protocols, such that Hashi
operates as long as fewer than f of the staking power is unresponsive
(liveness), and is secure as long as fewer than t of the staking power
is colluding. In the first version of Hashi, the team expects t to be in the
range of 33% to 50%, and f in the range of 20% to 33%. These values
might increase in future versions of Hashi.
| Parameter | Property | Hashi has this property while | Expected range in the first version |
|---|---|---|---|
f | Liveness | fewer than f of the staking power is unresponsive | 20% to 33% |
t | Security | fewer than t of the staking power is colluding | 33% to 50% |
Why does Hashi use a second signer?
In addition to the MPC signer, Hashi uses a second signer implemented with a cloud enclave that enforces policies independently of the MPC protocols, reducing the risk of collusion or supply-chain attacks.