Chain Reorganizations and Consensus
9 min readarticleIncludes quiz · 5 questions
In the early days of Bitcoin, a 1-block reorganization happened occasionally and was considered normal. A 6-block reorg would be a national-security-level event. The deeper the blockchain gets, the harder it is to rewrite history.
Chain Reorganization Basics:
- •Definition: Replacing blocks with a longer chain
- •Natural Occurrence: Happens with simultaneous blocks
- •Depth: Usually 1-2 blocks deep
- •Resolution: Longest chain (most work) wins
- •Frequency: Several times per month for 1-block
Consensus Rules:
- •Nakamoto Consensus: Follow chain with most proof-of-work
- •Block Validation: Every rule must be followed
- •No Voting: Code enforcement, not democracy
- •Fork Choice: Automatic chain selection
- •Finality: Probabilistic, not absolute
Key Takeaway
Chain reorganizations are why we wait for confirmations. Each new block built on top of a transaction makes that transaction exponentially more permanent.
Test Your Knowledge
5 questions · Passing score: 75%
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