BFTprotokoller

BFTprotokoller, or Byzantine Fault Tolerant protocols, are a class of distributed consensus algorithms designed to achieve agreement among a set of replicas even when some participants may behave arbitrarily or maliciously. They are used to maintain a replicated state machine across untrusted environments, enabling consistent ordering of operations in systems such as blockchains and distributed databases.

A core goal of BFT protocols is to ensure safety: no two honest replicas decide on different sequences of operations, and liveness: the system continues to make progress despite faults. In common models, the system consists of N replicas, and up to f of them can be Byzantine, with the typical requirement N ≥ 3f + 1. Protocols often assume partial or eventual synchrony and rely on cryptographic signatures and multiple rounds of message exchanges to form certificates that authorize a proposed value. Many designs are leader-based, where a primary proposes a value and other replicas vote to approve it, using view changes or rotated leadership to recover from a faulty leader.

Notable BFT protocols include Practical Byzantine Fault Tolerance (PBFT), which laid early foundations with a three-phase flow; Tendermint, which combines BFT consensus with a blockchain interface; and HotStuff, which introduces a modular, pipelined approach to improve simplicity and throughput. Other examples are SBFT and LibraBFT, developed for scalable, real-world deployments.

Applications of BFT protocols span blockchain platforms, replicated databases, and financial systems requiring strong consistency in adversarial environments. Trade-offs often involve communication complexity, latency, and scalability, with ongoing research aimed at reducing message overhead, improving dynamic membership handling, and leveraging threshold cryptography for efficiency.