What Is a “Fork” and How Does It Relate to the Potential for Replay Attacks?
A blockchain fork is a split in the network's history, resulting in two distinct chains. When a fork occurs, a valid transaction signed on the original chain might also be valid on the new chain, allowing for a "cross-chain replay attack." This is because the signature is for the same transaction data, which exists on both chains.
Solutions like Ethereum's EIP-155 prevent this by including a unique chain ID in the signed transaction data.
Glossar
Hard Fork
Disruption ⎊ A hard fork represents a radical divergence in a blockchain’s protocol, creating a permanent split and typically resulting in a new cryptocurrency.
Blockchain Fork
Fork ⎊ A blockchain fork represents a divergence in the blockchain's history, resulting in two or more separate chains.
Soft Fork
Evolution ⎊ A soft fork represents a backward-compatible alteration to a cryptocurrency's protocol, essentially a modification that doesn't invalidate older versions.
Replay Attacks
Vulnerability ⎊ Replay attacks, within decentralized systems, represent the unauthorized repetition of a valid transaction, posing a significant risk to consensus mechanisms and fund security.
Replay Attack
Vulnerability ⎊ A replay attack, within cryptocurrency, options trading, and financial derivatives, represents the unauthorized duplication of a valid transaction, potentially leading to double-spending or unintended execution of contracts.