What is Mysticeti (BFT)?

Mysticeti is a Byzantine Fault Tolerant consensus protocol developed for the Sui blockchain, designed to achieve low-latency consensus with minimal communication overhead. Mysticeti uses a DAG-based approach where validators propose blocks that reference previous blocks from other validators, forming a directed acyclic graph. Unlike protocols that require a designated leader for each round, Mysticeti allows multiple validators to propose blocks simultaneously in each round, increasing throughput and reducing the impact of any single slow validator. The protocol achieves consensus by identifying committed blocks through the DAG structure using a commit rule that requires observing sufficient support across rounds, enabling finalization without explicit voting messages.

Mysticeti achieves consensus latency as low as three message delays (approximately 390 milliseconds) in the common case, making it one of the fastest BFT protocols in production. The protocol tolerates up to one-third of validators being Byzantine while maintaining both safety and liveness. By allowing all validators to propose blocks in parallel rather than relying on a single leader per round, Mysticeti avoids the throughput bottleneck common in leader-based protocols and is more resilient to slow or crashed leaders. The uncertified DAG approach — where blocks do not need explicit certification before being referenced — further reduces latency compared to certified DAG protocols like DAG-Rider or Bullshark.

Mysticeti was developed by researchers at Mysten Labs and deployed on the Sui mainnet in 2024, replacing the earlier Narwhal and Bullshark consensus components. Sui is a high-performance Layer 1 blockchain designed for low-latency applications, built using the Move programming language. The transition to Mysticeti significantly reduced consensus latency on the network. The protocol emerged from academic research and was published as a peer-reviewed paper. Sui's object-centric data model allows simple transactions involving owned objects to bypass consensus entirely, with Mysticeti handling only transactions that involve shared objects, further optimizing overall network performance.