Replay Attack
When a valid transaction from one chain is maliciously or accidentally broadcast and accepted on another chain after a fork.
A replay attack can happen after a chain split when the same signed transaction is valid on both resulting chains. If addresses, signatures, and scripts remain compatible, someone can rebroadcast the transaction on the other chain and move the corresponding coins there too.
Mitigations include protocol-level replay protection, chain-specific signature hashing, different address formats, and wallet workflows that split coins before spending. Without these protections, users must be careful when moving funds around a contentious fork.
Related terms
4 linkedExplore connected entries beyond the alphabetical index.
Fork
→A fork is a blockchain divergence caused by competing blocks, software changes, or incompatible consensus rules.
Chain Split
→A permanent divergence into two or more incompatible blockchain histories.
Replay Protection
→Protocol or wallet techniques that prevent transactions from one chain being valid on another after a split.
Wallet
→Software or hardware that manages crypto keys, creates addresses, signs transactions, and shows blockchain activity.
All terms and definitions may update as the Cryptionary improves.
