question about signature request

Question

How can I create this signature?

along with nonce,value,contract?

Answer 1

As you added the ethers.js tag to your question, here an example how to do it with ethers. You can use ethers.utils.solidityKeccak256 to hash nonce, value, and address into a message you can sign using signMessage.

const { ethers } = require('ethers');

const provider = new ethers.providers.JsonRpcProvider(YOUR_RPC_URL);
const signer = new ethers.Wallet(YOUR_PRIVATE_KEY, provider);
// get latest nonce for your account
const nonce = await provider.getTransactionCount(signer.address, 'latest');
// set value to 0 if you just want to sign without sending ether
const value = 0; 

const message = ethers.utils.solidityKeccak256(
  ['uint256', 'uint256', 'address'],
  [nonce, value, CONTRACT_ADDRESS]
);

const signature = await signer.signMessage(ethers.utils.arrayify(message));