Am working on a project & am keen to keep password-storage secure from the start. In the idea phase, but this is roughly what I intend to use.
class Crypto {
public function hash1($string, $salt) {
return hash('sha512', $string . $salt);
}
public function hash2($string, $salt) {
return hash('sha512', $salt . $string);
}
public function compareToHash($string, $salt, $hash1, $hash2) {
return($this->hash1($string, $salt) === $hash1 && $this->hash2($string, $salt) === $hash2);
}
}
As you can see I am trying to avoid collisions. Is this an effective way, it seems awfully simple and I wonder if I am missing something.
Thanks.
If you want to make your password storage secure from the start, you should not use
sha512or any other fast hash algorithm, instead use a key derivation function like BCrypt.The problem with fast algorithms is, that you can calculate 80 Mega sha512-hashes per second with common hardware (in 2012). That makes it possible to brute-force a whole english dictionary with about 500000 words, in a few milliseconds! Other algorithms are even faster.
BCrypt was especially designed to hash passwords, and is therefore slow (needs some computing time). With a cost factor you can adapt the needed time to future (and therefore faster) hardware.
Using BCrypt can be as easy, as using the sha512 hash. It's recommended to use a well established library like phpass, and if you want to understand how it can be implemented, you can read this article, where i tried to explain the most important points.
Your scheme with two separate hashes will not increase security, because collisions with sha512 are never the problem. In the worst case it even weakens security, because you have to store both hashes, so an attacker has two related informations about the hashed password.