consensusalgoritmes

Consensusalgoritmes are protocols for achieving agreement among distributed processes or nodes. They enable a group of participants to decide on a single value or a sequence of values, even in the presence of failures or, in some cases, malicious actors. They are central to replicated state machines, fault-tolerant databases, and many blockchain platforms.

Core properties typically include agreement (all non-faulty nodes decide the same value), termination (every non-faulty node eventually decides), and validity (the decided value is derived from proposals by some node). In Byzantine settings, algorithms must tolerate arbitrary faults and ensure safety despite potentially faulty or adversarial participants.

Models differ by timing assumptions. Synchronous or partially synchronous systems allow progress under bound conditions, while fully asynchronous systems face fundamental limits. The FLP result shows that deterministic consensus is impossible to guarantee in a purely asynchronous network with even one faulty process, prompting reliance on randomness or partial synchrony in practical protocols.

Prominent examples span crash-fault-tolerant and Byzantine-fault-tolerant families. Paxos and its variants (including Multi-Paxos) target crash faults, with Raft offering a more approachable design. Byzantine fault tolerance includes protocols such as PBFT (Practical Byzantine Fault Tolerance), Tendermint, and HotStuff. Modern protocols often emphasize safety with robust liveness through leadership changes or view changes.

Applications include distributed databases, coordination services, and blockchain networks where all participants maintain a consistent history. Key concerns for consensusalgoritmes are latency, throughput, scalability, dynamic membership, and secure key management, all of which influence practical deployment.