Metamask: Integrating KMS with Ether _signTypedData (EIP712)

Here is an article about integrating Metamask with Ethers signed printed data:

KMS Integration with Ethers: A Step-by-Step Guide to Signed Printed Data

In recent years, the use of Key Management Systems (KMS) in blockchain development has become increasingly popular. One such system is Amazon KMS (Amazon Web Services Key Management Service), which provides secure key management and encryption services for various applications.

A common requirement when developing smart contracts on Ethereum is the ability to sign recorded data using a private key stored in an environment variable. In this article, we will explore how to integrate KMS with Ethers to achieve signed verification of recorded data.

Why sign the data entered?

Before we dive into the integration process, let’s briefly discuss the importance of signed printed data (EIP712):

• Unambiguous: The signature confirms that the data was created and signed by the holder.

• Non-repudiation: Ensures that the sender cannot deny having created the data.

Environment variables for private keys

To securely store private keys, you should use environment variables. This approach allows users to manage their keys without exposing them in the code.

// Setting the environment variable
const privateKey = process.env.KEY_PRIVATE;

Configuring KMS with Ethers

To integrate Metamask with Ethers, we will use the “ethers” and “ethers.js” packages. First, install the required packages:

npm install ether @types/ethers

Next, set up your Ethereum wallet and account. For this example, let’s assume you have a MetaMask wallet.

Generating Signed Print Data

We will use the “ethers/web3” package to generate signed print data using KMS. First, create a contract with a function that generates signed print data:

// Example EIP-712 structure definition for print data
constant structure = {
fields: [
{name: 'name', type: 'string'},
{name: 'version', type: 'number'}
]
};
export const typedDataStruct = Structure;
export function generateSignedTypedData(data) {
// Generate a random signature
const sig = crypto.createSign('SHA256');
sig.update(Buffer.from(typedDataStruct, 'utf8'));
// Sign the data using a private key (environment variable)
const signature = sig.sign(private key);
return {signature};
}

Signing the saved data using metamask

Now that we have the “generateSignedTypedData” function, let’s integrate it into your contract. First, create an interface for the signed printed data:

// Define the EIP-721 structure for the sample contract
const structure = {
fields: [
{name: 'name', type: 'string'},
{name: 'version', type: 'number'}
]
};
export const EIP721 = Structure;
export function generateSignedTypedData(data) {
return generateSignedTypedData({name: data.name, version: data.version});
}

Finally, we can use the “EIP721” interface to sign the data stored in our contract:

// Sample contract code snippet (Node.js)
import { EIP721 } from './interface';
const contract = new ethers.Contract('0x... contract address...', EIP721);
async function function1() {
const data = {name: 'Example Agreement', version: 1};
try {
const signature = await contract.generateSignedTypedData(data);
console.log(Signature: ${signature});
} catch (error) {
console.error(error);
}
}

Running the Code

To run this code, you will need to set up a local Ethereum blockchain using MetaMask or another compatible wallet. Once you have a valid account and a configured private key, you can compile your EIP-721 contract and use it with Metamask.

“`bah

Developing the npx security helmet.