Metamask signature verification for Web3.js typed data objects

As interest in Web3.js and WebAssembly has grown, the use of Metamask has become more and more popular. One aspect of Metamask that can be challenging for developers using standard typed data objects is ensuring signature integrity. In this article, we’ll take a closer look at how to compare the same signature used when signing with Metamask with the signature obtained using the signTypedData_v4 method.

Standard typed data object and characters

Let’s say you have a standard typed data object that uses Metamask like this:

Constant order = {
// Your data here...
};
// Using JSON.stringify to serialize the object before signing
const sig = web3.eth.accounts.sign(JSON.stringify(order), 'your private key_here');

In this case, JSON.stringify converts the Order object to a JSON string representation. The web3.eth.accounts.sign method then uses this JSON string as input to sign the data with your private key.

SignTypedData_v4 method

The signTypedData_v4 method, which is part of Web3.js, provides a more secure and standardized way to sign data. This method uses the same principles as Metamask’s signature verification, but with additional security features:

Constant order = {
// Your data here...
};
// Using signTypedData_v4 to verify the signature
const { sig } = web3.eth.accounts.signTypedData_v4(order, 'your_private_key_here');

Here, web3.eth.accounts.signTypedData_v4 takes the same inputs as above and generates a signature for the signed data.

Comparing signatures

Now let’s compare the two signatures obtained using both methods:

const expectedSig = web3.eth.accounts.sign(JSON.stringify(order), 'your private key here');
console.log(expectedSig); // Output: your actual signature
const actualSig = web3.eth.accounts.signTypedData_v4(order, 'your private key here');
console.log(currentSig); // Output: Your actual signature (with additional security features)

As you can see, the actualSig obtained using signTypedData_v4 is identical to the expectedSig obtained via sign. This is because both methods use the same input data and private key.

Metamask signature verification

To verify Metamask’s signature verification process, you can compare the two signatures:

const expectedSig = web3.eth.accounts.sign(JSON.stringify(order), 'Your private key here');
console.log(expectedSig); // Output: Your actual signature (with Metamask)
const actualSig = web3.eth.accounts.signTypedData_v4(order, 'Your private key_here');
console.log(currentSig); // Output: same as expectedSig

In this case, you can see that both signatures are identical, indicating that Metamask’s verification process is working properly.

Conclusion

To summarize, there are similarities between checking signature integrity using signTypedData_v4 and Metamask’s signature verification process. Both methods use the same input data and private key to generate a signature. The main difference is the underlying implementation, which provides additional security features via signTypedData_v4. By comparing the signatures obtained using both methods, you can verify that your signed data was indeed correctly verified by Metamask.

When using standard-typed data objects with Web3.js, it is important to ensure that the signature verification process is correct. By following these best practices, you can write more secure and reliable code for your web applications.

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