ecrecover en solidez devolviendo dirección nula [duplicado]

Necesito ayuda con la verificación de la dirección de Ethereum. Estoy siguiendo el tutorial sobre cómo firmar y validar la dirección de Ethereum. Código GitHub . Estoy confundido por mi resultado real de la dirección después de ejecutar loginContractInstance.recoverAddr.call(addr, fixed_msg_sha, v_decimal, r,s, function(err, actual) {porque devuelve nulo.

Aquí está mi código backend a continuación,

// Unlock account before the login attempt
web3.personal.unlockAccount(req.body.address, req.body.password, 100, function(error, unlocked) {
    console.log(`>>>>> Login - User is unlocked: ${unlocked}`);
    if (unlocked) {

        // Signing/ Encryption
        const addr = req.body.address;
        const msg = req.body.password;
        const hex_msg = '0x' + toHex(msg);
        let signature = web3.eth.sign(addr, hex_msg);

        console.log(`address -----> ${addr}`);
        console.log(`msg ---------> ${msg}`);
        console.log(`hex(msg) ----> ${hex_msg}`);
        console.log(`sig ---------> ${signature}`);

        const r = signature.slice(0, 66)
        const s = '0x' + signature.slice(66, 130)
        const v = '0x' + signature.slice(130, 132)
        const v_decimal = web3.toDecimal(v);

        console.log(`r -----------> ${r}`);
        console.log(`s -----------> ${s}`);
        console.log(`v -----------> ${v}`);
        console.log(`vd ----------> ${v_decimal}`);

        // Validation/Decryption
        const fixed_msg = `\x19Ethereum Signed Message:\n${msg.length}${msg}`
        const fixed_msg_sha = '0x' + web3.sha3(fixed_msg)

        loginContractInstance.isSigned.call(addr, fixed_msg_sha, v_decimal, r, s, function (err, signed) {
            console.log(`>>>>> Login - Signature: ${signed}`);

            if (signed) {
                // Saving login attempt
                loginContractInstance.successfulLogin.sendTransaction(req.body.address, req.body.password,
                    {from:'6ded1c5b448819a6cde4293e33fbe54583ef5c52', gas:200000},
                    function(err, transactionHash) {
                        if (!err) {
                            console.log(`>>>>> Login - login details (${addr}, ${msg}) successfully saved @ ${transactionHash}`);
                            console.log(`>>>>> Login - Successfully login`);

                        } else {
                            console.log(`>>>>> Login - login transaction failed: ${err}`);
                        }

                        // set primary account to mine
                        web3.eth.coinbase = req.body.address;

                        console.log(`>>>>> Login - Current User: ${web3.eth.coinbase} is logged in`);

                        var balanceWei = web3.eth.getBalance(req.body.address).toNumber();
                        var balance = web3.fromWei(balanceWei, 'ether');
                        res.json({
                            allowedLogin: true,
                            address: req.body.address,
                            balance: balance,
                            token: generateToken(addr)
                        });

                    });
            } else {
                loginContractInstance.recoverAddr.call(fixed_msg_sha, v_decimal, r,s, function(err, actual) {
                    console.log(`>>>>> Login - Failed login: Signature not matched:${addr} = ${actual}`);
                    saveFailedLoginAttempts(loginContractInstance, req, res);
                });
            }
        });
    } else {
        console.log(`>>>>> Login - Failed login: User is locked`);
        saveFailedLoginAttempts(loginContractInstance, req, res);
    }

});

Y mi contrato inteligente,

contract Login {

event LoginAttempt(address sender, string password);

address private sender;
string private password;

function successfulLogin (address _sender, string _password) public {
    LoginAttempt(_sender, _password);
    sender = _sender;
    password = _password;
}

function failedLogin (address _sender, string _password) public {
    LoginAttempt(_sender, _password);
}

function recoverAddr(bytes32 msgHash, uint8 v, bytes32 r, bytes32 s) public pure returns (address) {
    return ecrecover(msgHash, v, r, s);
}

function isSigned(address _addr, bytes32 msgHash, uint8 v, bytes32 r, bytes32 s) public pure returns (bool) {
    return ecrecover(msgHash, v, r, s) == _addr;
}

Aquí está el resultado de esa llamada de función en mi consola,

¿Alguien puede ayudar en lo que me estoy perdiendo?

EDITAR

He corregido la función recoveryAddr.call para usar la entrada correcta. También descubrí que fixed_msg_shael problema es mío porque 0xagregué const fixed_msg_sha = '0x' + web3.sha3(fixed_msg). se imprimió así0x0xf348f6a3d221a5e7e851292474330ca6e6cf6ad54572ee114233ab9b9225ab4f

Ahora el problema ha cambiado para devolver una dirección 0x,