Replay Attack
security · fork
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
Fork
→A fork is a blockchain divergence caused by competing blocks, software changes, or incompatible consensus rules.
blockchain · event
Chain Split
→A divergence in which nodes accept competing block histories; it may resolve by reorganization or persist as separate networks.
blockchain · governance
Replay Protection
→Consensus or wallet techniques that stop or reduce unintended reuse of the same signed transaction across split chains.
security · fork
Wallet
→Software or hardware that manages signing credentials, addresses, transactions, and access to blockchain assets.
wallet · security