Signature Replay and ECDSA Pitfalls

This lesson is for enrolled learners

The concept Off-chain signatures (a user signs a message with their wallet without sending a transaction, and a contract verifies that signature later) are everywhere in modern dApps — gasless meta-transactions, permit-based token approvals (ERC-2612), order books, and voting delegation. They're efficient because the user doesn't pay gas to sign, but every signature-based system introduces a class of bugs that……

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