Distributed Consensus
Definition
Distributed consensus is the process by which multiple nodes in a distributed system agree on a shared state or sequence of events, even when some nodes fail, messages are delayed, or participants behave maliciously.
Core Ideas
Why It Is Hard
The source notes list several reasons:
- nodes may crash
- nodes may be malicious
- networks have latency and faults
- not every participant sees the same information at the same time
Classic Difficulty
Consensus theory includes famous impossibility and fault-tolerance results, such as Byzantine fault scenarios and the limits of deterministic consensus in faulty systems.
Blockchain Twist
The blockchain notes emphasize that Bitcoin-style systems approach consensus differently:
- add incentives
- embrace randomness
- tolerate probabilistic rather than absolute finality
This differs from classic distributed protocols like Paxos, which focus on consistency guarantees in more bounded environments.
Relationships
- Proof of Work — proof of work is one mechanism for reaching distributed consensus without trusted identity
- Cryptocurrency Fundamentals — consensus is central to how public blockchains avoid double-spending and fork chaos
- System Design — consensus is also a broader systems topic beyond blockchain
References
- 2.2 Distributed Consensus
- 2.3 Consensus without identity