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Immutability

blockchain
security

The practical resistance of confirmed blockchain history to alteration, created by consensus, replication, and economic cost.

Also known as
tamper-resistance
append-only ledger
1
concept

Immutability means that once data is deeply confirmed, changing it becomes impractical rather than merely inconvenient. In proof-of-work systems, an attacker would need to redo enough work to replace history and convince nodes to accept the heavier valid chain.

2
limits

Blockchain immutability is not absolute. Short reorganizations, consensus bugs, emergency interventions, or deliberate hard forks can affect what history a community recognizes.

Conceptual links

Related terms

4 linked

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All terms and definitions may update as the Cryptionary improves.