What is SMFT?

SMFT (Soft Majority Fault Tolerance) is the consensus mechanism used by the Everscale blockchain (formerly Free TON), which extends traditional BFT to support dynamic and elastic validator sets. In standard BFT protocols, safety requires that fewer than one-third of validators are malicious, and all validators must participate in every consensus round. SMFT relaxes this requirement by introducing a "soft majority" concept where the protocol can operate correctly even when not all validators are online, as long as the majority of participating validators are honest. The protocol divides the network into workchains and thread groups, with each group running its own consensus instance. Validators rotate between groups, and the protocol uses BFT-style voting within each group.

SMFT is designed for the specific requirements of Everscale's multi-threaded, multi-workchain architecture, where parallelism is essential for scalability. The protocol maintains safety guarantees while accommodating the dynamic nature of a sharded network where validator subsets change over time. Each thread within a workchain runs its own consensus process, allowing the network to process transactions in parallel across many threads. The soft majority approach means the network can continue making progress even when some validators are temporarily offline, improving liveness compared to strict BFT protocols that halt when too many validators are unresponsive. Block times are in the low single-digit seconds range.

SMFT runs on the Everscale network, which originated from the open-source code of the Telegram Open Network (TON) after Telegram abandoned the project due to SEC regulatory action. Everscale launched in May 2020 and has since developed independently from the separate TON revival (now called The Open Network). The blockchain uses the TVM (TON Virtual Machine) for smart contract execution and supports dynamic sharding, where the number of threads can increase or decrease based on load. The SMFT consensus was designed by the Everscale development community to support this highly parallelized architecture while maintaining the safety properties needed for a production blockchain network.