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Signing Structured Messages with Ethereum: signTypedData_v4 Guide
When interacting with the Ethereum blockchain, you need to verify the authenticity and integrity of messages sent between nodes. One way to do this is to use the Web3j library, which provides a JavaScript API for interacting with the Ethereum network.
Especially when working with structured messages like signTypedData_v4, you often need to manually sign these messages. In this article, we will look at how to modify your code to use signTypedData_v4 and provide guidance on what has changed compared to signTypedData_v3.
What is signTypedData_v4?
signTypedData_v4 is a new Ethereum standard for signing structured messages. It builds on the success of signTypedData_v3, which was introduced in 2020. The main difference between these two standards is Web3j’s built-in support for cryptographic primitives such as ECDSA and Ed25519.
Why does my code work for ‘signTypedData_v3’ but not for ‘signTypedData_v4’?
When using ‘signTypedData_v3’, the code relies on a custom implementation of the Ethereum Smart Contract Signature Algorithm (ECDSA). This requires manual processing of cryptographic operations, which can lead to errors.
In contrast, signTypedData_v4 uses Web3j’s built-in support for ECDSA and other cryptographic primitives. These libraries automatically handle basic cryptographic operations, ensuring that your code is more reliable and efficient.
Modify your code to use signTypedData_v4
To start using signTypedData_v4, you need to modify your Web3j code accordingly. Here are some steps you need to follow:
- Import the right library: Make sure you have imported the “web3 signer” module from Web3j, which provides a “Signer” class that can handle structured messages.
- Create a new instance of Signer
: Create a new instance of “Signer” and specify the Ethereum network (e.g. “mainnet”).
- **Use the “signTypedData_v4” method: Pass the message data to the “signTypedData_v4” method, which handles signature generation and verification.
- Specify the cryptographic algorithm: Use the built-in ECDSA or Ed25519 support of the
Web3j' library by passing a string specifying the algorithm (e.g. "ecdsa" or "ed25519").
- Use the “key” option: to specify a custom key: If you have a custom key pair, you can pass it to the “signTypedData_v4” method using the “key” option (e.g. “{ key: “custom key” }`).
Here are some sample code to get you started:
const Web3 = request('web3');
const signer = new Web3.signer('mainnet');
const message = {
// Your structured message data
};
signTypedData_v4(message, { algorithm: 'ecdsa', key: 'your-custom-key' })
.then((signature) => console.log(signature))
.catch((error) => console.error(error));
Conclusion
Signing structured messages with Ethereum using “signTypedData_v4” is a more reliable and efficient approach compared to custom implementations of the ECDSA algorithm. You can reduce errors and increase overall performance by using Web3j’s built-in support for cryptographic primitives.
Be sure to follow secure coding best practices, such as securely managing private keys and implementing appropriate error handling mechanisms.