Consensus Attacks (Global)
High-quality technical overview of Consensus Attacks in the context of blockchain security.
Roles: 1. Reorg protection (Absolute finality). 2. Fast Sync (Skipping script verification). 3. Denial-of-Service (DoS) prevention. Types: Hardcoded (Static), Consensus-driven (Dynamic). Issues: Centralization concerns (who chooses the points?), Security-liveness trade-offs.
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🧒 Wyjaśnij jak 5-latkowi
Imagine a [blockchain](/pl/terms/blockchain) is a very long book that everyone is writing together. A checkpoint is like a teacher coming by and 'stamping' the first 100 pages, saying: 'This part is definitely correct, and you are not allowed to go back and change any words on these pages.' This makes it easier for new students to catch up because they can just trust the stamped pages and focus on reading what's being written right now.
🤓 Expert Deep Dive
Checkpoints serve as a defense against 'Deep Reorg' attacks, such as those that could be launched by a malicious miner with 51% hash power trying to rewrite weeks of history. In early Bitcoin versions, checkpoints were added periodically by developers to prevent Sybil attacks during the network's infancy. In modern Proof-of-Stake (PoS) systems, 'Dynamic Checkpointing' (Finality) is built into the protocol. For example, in Ethereum, every 'Epoch' (~6.4 minutes) of blocks is considered for a checkpoint by a quorum of validators. Once 2/3 of the stake votes for a checkpoint, it becomes 'Finalized', and any validator who tries to vote for a conflicting chain would have their entire stake 'Slashed' (destroyed).