# 签名：EIP712

By [point](https://paragraph.com/@point) · 2022-05-03

---

    //使用web3.js和eth-sig-util生成签名
    import Web3 from "web3";
    var sigUtil = require("eth-sig-util")
    
    const typedData = {
            //定义数据格式
            types: {
              //固定格式,不要动,并且字段一个都不能少
              //name:contract name
              //vaersion:版本号,如1.0随意
              //chainId:当前链chainId
              //verifyingContract:合约地址
              EIP712Domain: [
                {name: 'name', type: 'string'},
                {name: 'version', type: 'string'},
                {name: 'chainId', type: 'uint256' },
                {name: 'verifyingContract', type: 'address' },
              ],
              //自定义自己业务的数据格式
              Mail: [
                {name: 'from', type: 'address'},
                {name: 'to', type: 'address'},
                {name: 'value', type: 'uint256'},
              ],
            },
              //上面定义的数据格式具体内容
            domain: {
              name: 'Demo',
              version: '1.0',
              chainId:'1',
              verifyingContract:'0xf8e81D47203A594245E36C48e151709F0C19fBe8'
            },
            primaryType: 'Mail',
              //具体的业务字段,需要和上面的Mail格式对应
            message: {
              from: "0xE3a463d743F762D538031BAD3f1E748BB41f96ec",
              to: "0x39Ef50bd29Ae125FE10C6a909E42e1C6a94Dde29",
              value: 1234234145789,
            },
          }
          //生成签名 privateKey 是钱包账户的秘钥
          var privateKeyHex = Buffer.from(privateKey, 'hex')
          var signature = sigUtil.signTypedData_v4(privateKeyHex, {data: typedData})
    }
    

    // SPDX-License-Identifier: MIT
    pragma solidity ^0.8.0;
    import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/cryptography/ECDSA.sol";
    import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/cryptography/draft-EIP712.sol";
    
    contract MyContract is EIP712 {
           
        constructor(string memory name, string memory version) EIP712(name, version) {}
        
         //生成签名的业务参数和生成的签名
        function recoverV4(
            address from,
            address to,
            uint256 value,
            bytes memory signature
        ) public view returns (address) {
            bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
            //需要和js中的type中业务的数据格式对应
            keccak256("Mail(address from,address to,uint256 value)"),
               from,
                to,
                value
            )));
            return ECDSA.recover(digest, signature);
        }
    }

---

*Originally published on [point](https://paragraph.com/@point/eip712)*