Security//Replay Attack

- Replaying a transaction signed for one chain on another chain with the same chainId.

Replaying a transaction signed for one chain on another chain with the same chainId.

Chain ID in the signature prevents cross-chain replay: different chains → different signature hashes (EIP-155)

Even with same chainId: nonce mismatch blocks replay — if the target chain's account nonce is ahead, the old nonce is rejected.

EIP-712 goes further: adds verifyingContract address to the signed domain — prevents cross-contract replay on the same chain.