Question

So I’ve been reading a lot about encryption in PHP. So much that I am not sure exactly what’s a really good method to securely store login information.

However, the following function is what I came up with:

function loginHash($username, $password){
    $salt = str_split($password,(strlen($password)/2)+1);
    $hash = hash('whirlpool', $username.$salt[0].'centerSalt'.$salt[1]);
    return $hash;
}

Am I doing it the right way? It’s used for authenticating a password combined with a username, and the ability to compare the generated hash with the one stored in a database to verify a login.

Answer 1

Encrypting != Hashing. They both are generally accepted to be in the category of Cryptography, but when something can be encrypted, it can be decrypted, which is not the case in Hashing. Hashing is just hashing, and that’s it.

The salt is indeed not properly constructed. It should be x-bytes read from /dev/urandom with a fopen() call. For example, 16 bytes of salt is what I personally use. This prevents rainbow table attacks effectively.

To make things more secure, use a secret key, too. For example:

$hashedPassword = hash_hmac('whirlpool',$password.$salt,$key);

The $key is simply random data. You could generate a 64 kB file, for instance, that is called “key.bin” in a hidden folder above the document root and use file_get_contents() before the hash process.

Why to use secret keys? If you store the hashes and salts in a database and the key in the filesystem, then this prevents anyone from cracking your hash if they get their hands on your stored hashes and salts. So, an attacker would need to crack into both the database and the filesystem to crack your hashes, but notice that it’s pointless for anyone to crack your hashes anymore if they have already cracked your whole application, which implies that your hashing scheme is good.