How long would it take to brute force the AES encryption?

Question

I'm trying to write a secure code that can keep my site users passwords as safe as possible. Now I'm fairly new to encryption and would like some professional opinions and suggestions. As well as a raw estimate of how long it would take to brute force my current encryption method.

So my encryption begins with creating a random SALT value as such

$salt = dechex(mt_rand(0, 2147483647)) . dechex(mt_rand(0, 2147483647)); 

After the SALT value is create it is hashed using SHA-256 as such

$password = hash('sha256', $_POST['bindPass'] . $salt);

After the $password hash is create I re-hash the values to secure them farther

 for($round = 0; $round < 656757; $round++) 
 { 
     $password = hash('sha256', $password . $salt); 
 } 

Now after rehashing is done the Encryption is bound to a function and is added directly into PDO Insert query. Here is the Encryption function.

function encrypt_cpass($in)
{

    $iv_size = mcrypt_get_iv_size(MCRYPT_TWOFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $enc = mcrypt_encrypt(MCRYPT_TWOFISH,ENCRYPT_KEY, $in, MCRYPT_MODE_ECB, $iv);
    $enc = base64_encode($enc);
    return $enc;
 } 

And finally the PDO part

$query_params = array( 
    ':password' => encrypt_cpass($password),
            ..........
} 

I can't say I get bad performance with the following code and the script, but I am more worried that I may be doing the password securing not the right way and it may eventually be broken. So again if you have any suggestions or could point me to some good resources please post them.

Cheers.

Answer 1

There are a few things here. First and foremost, you don't need to encrypt a hash. The point of a hash is to protect the original password. Symmetric encryption on top of that doesn't add much since it is fairly likely that the key will be compromised if your servers are compromised anyway (which should be the only way that someone walks off with your user DB).

Second, if you are using a random IV but I don't see it being stored. I'm not that familiar with mcrypt specifically, so forgive me if it takes care of storing the IV in some format with the encrypted output, but if you don't store the IV in some way, decryption will be impossible.

Third, use a secure, slow cryptographic hash like bcrypt rather than SHA256 and you will get much further security from the hash itself. Speed in hashing is bad and encryption is unnecessary and ineffective. Use a slow enough hash that generating rainbow tables is cost prohibitive but verification is not and you should be fine.