Retrieve public key and check the signature with web3

Question

I create a transaction with signTransaction and I have an output like this:

"signedTx": {
    "messageHash": "0x..",
    "v": "0x..",
    "r": "0x..",
    "s": "0x..",
    "rawTransaction": "0x....."
},

Now I want to retrieve public key using v r and s And verify the signature

Answer 1

you can use ecRecover function in [email protected]

web3.eth.personal.ecRecover(dataThatWasSigned, signature [, callback])

Example

web3.eth.personal.ecRecover("Hello world", "0x30755ed65396facf86c53e6217c52b4daebe72aa4941d89635409de4c9c7f9466d4e9aaec7977f05e923889b33c0d0dd27d7226b6e6f56ce737465c5cfd04be400").then(console.log);

"0x11f4d0A3c12e86B4b5F39B213F7E19D048276DAe"

Or you can use ethereumjs-utils library function ecrecover

Edit You can use this to recover public address

const publicKey = util.ecrecover(util.sha3('test'), sig.v, sig.r, sig.s);
const address = util.pubToAddress(publicKey).toString('hex');