Signing with EIP191

Use EIP191 eth_personal_sign to sign a message instead of a transaction or raw signature.

This can be done with

LitActions.ethPersonalSignMessageEcdsa({ message, publicKey , sigName }); 

It will prepend "\x19Ethereum Signed Message:\n" to the message and then hash and sign it according to https://eips.ethereum.org/EIPS/eip-191.

Lit Action code:

export const litActionCode = `
(async () => {
  const sigShare = await LitActions.signEcdsa({
    toSign: dataToSign,
    publicKey,
    sigName,
  });
})();
`;

Lit SDK code:

const litActionSignatures = await litNodeClient.executeJs({
  sessionSigs,
  code: litActionCode,
  jsParams: {
    dataToSign: ethersUtils.arrayify(
      ethersUtils.keccak256([1, 2, 3, 4, 5])
    ),
    publicKey: pkpPublicKey,
    sigName: "sig",
  },
});

const dataSigned = `0x${signature.dataSigned}`;
const encodedSig = ethersUtils.joinSignature({
  v: signature.recid,
  r: `0x${signature.r}`,
  s: `0x${signature.s}`,
});

const recoveredPubkey = ethersUtils.recoverPublicKey(dataSigned, encodedSig);
console.log("Recovered uncompressed public key: ", recoveredPubkey);

const recoveredAddress = ethersUtils.recoverAddress(dataSigned, encodedSig);
console.log("Recovered address from signature: ", recoveredAddress);

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