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166 - OZ ECDSA

OpenZeppelin ECDSA: provides functions for recovering and managing Ethereum account ECDSA signatures.

These are often generated via web3.eth.sign, and are a 65 byte array (of type bytes in Solidity) arranged the following way: [v (1), r (32), s (32)].

The data signer can be recovered with ECDSA.recover, and its address compared to verify the signature.

Most wallets will hash the data to sign and add the prefix \x19Ethereum Signed Message:\n, so when attempting to recover the signer of an Ethereum signed message hash, you’ll want to use toEthSignedMessageHash.

The ecrecover EVM opcode allows for malleable (non-unique) signatures.

This library prevents that by requiring the s value to be in the lower half order, and the v value to be either 27 or 28.

Slide Screenshot

166.jpg

Slide Text

  • ECDSA Signatures
  • Signature -> (v, r, s)
  • v=1B, r=32B, s=32B
  • recover(msgHash, signature) -> signerAddress
  • EVM ecrecover -> Malleable
  • OZ ECDSA -> v=27/28, s=lower

References

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