How to decrypt signed message with web3 and public key

Question

I want to verify my user before the server sends him information.

So I want the user to sign a message using his private key, then the server decrypt that signature to verify the user is indeed the owner of a wallet address.

So I used the following on the client side

web3.eth.personal.sign

I am not sure what I can use on the server side to decrypt that signature and verify the original message and sender address.

Thank you for advance.

Answer 1

Most answers for verification are outdated. Something like the following worked for me.

    var msg = Buffer.from(msgstr);
    const prefix = Buffer.from("\x19Ethereum Signed Message:\n");
    var prefixedMsg = Buffer.concat([prefix, 
    Buffer.from(String(msgstr.length)), msg]);
    
    prefixedMsg = Web3.utils.keccak256(prefixedMsg);
    prefixedMsg = prefixedMsg.substring(2);
    prefixedMsg = Uint8Array.from(Buffer.from(prefixedMsg, 'hex'));
    var pub = ethJsUtil.ecrecover(prefixedMsg , vrs.v, vrs.r, vrs.s);
    var addrBuf = ethJsUtil.pubToAddress(pub);
    var addr = ethJsUtil.bufferToHex(addrBuf);