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Signing within a Lit Action using EIP-191

Overview​

Lit Actions offer the ability to use EIP-191 to sign a message instead of a transaction or raw signature. This is done with the Lit Actions method ethPersonalSignMessageEcdsa.

It will prepend to your message: "\x19Ethereum Signed Message:\n" and the length of the message, then hash and sign it according to the EIP-191 standard.

Prerequisites​

Complete Code Example​

The complete code example is available in the Lit Developer Guides Code Repository. There you can find a Node.js and browser implementation of this example code.

Example Lit Action​

The return value of ethPersonalSignMessageEcdsa (the sigShare variable in this example) is set to a boolean value of true if the signature was successfully generated, and false otherwise. The Lit Action will also return the complete signature as an object under the sigName key.

const _litActionCode = async () => {
  try {
    const sigShare = await LitActions.ethPersonalSignMessageEcdsa({
      message: dataToSign,
      publicKey,
      sigName,
    });
    LitActions.setResponse({ response: sigShare });
  } catch (error) {
    LitActions.setResponse({ response: error.message });
  }
};

export const litActionCode = `(${_litActionCode.toString()})();`;

Summary​

This guide demonstrates how to sign an EIP-191 message using Lit Actions.

If you'd like to learn more about Lit Actions, check out the Lit Actions SDK, or our Advanced Topics section on Lit Actions.

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