Simple bcrypt object to wrap crypt() with.

bcrypt.php

<?php

// Originally by Andrew Moore
// Src: http://stackoverflow.com/questions/4795385/how-do-you-use-bcrypt-for-hashing-passwords-in-php/6337021#6337021
//
// Heavily modified by Robert Kosek, from data at php.net/crypt

class Bcrypt {
  private $rounds;
  private $prefix;
  private $salt_prefix;
  
  public function __construct($prefix = '', $rounds = 12) {
    if(CRYPT_BLOWFISH != 1) {
      throw new Exception("bcrypt not supported in this installation. See http://php.net/crypt");
    }

    $this->rounds = $rounds;
    $this->prefix = $prefix;
    
    // Determine if this version of PHP has the Bcrypt fix
    $this->salt_prefix = version_compare(PHP_VERSION, '5.3.7') >= 0 ? '$2y' : '$2a';
  }

  public function hash($input) {
    $hash = crypt($input, $this->getSalt());

    if(strlen($hash) > 13)
      return $hash;

    return false;
  }

  public function verify($input, $existingHash) {
    $hash = crypt($input, $existingHash);

    return $hash === $existingHash;
  }

  private function getSalt() {
    // the base64 function uses +'s and ending ='s; translate the first, and cut out the latter
    return sprintf('%s$%02d$%s', $this->salt_prefix, $this->rounds, substr(strtr(base64_encode($this->getBytes()), '+', '.'), 0, 22));
  }
  
  private function getBytes() {
    $bytes = '';

    if(function_exists('openssl_random_pseudo_bytes') &&
        (strtoupper(substr(PHP_OS, 0, 3)) !== 'WIN')) { // OpenSSL slow on Win
      $bytes = openssl_random_pseudo_bytes(18);
    }

    if($bytes === '' && is_readable('/dev/urandom') &&
       ($hRand = @fopen('/dev/urandom', 'rb')) !== FALSE) {
      $bytes = fread($hRand, 18);
      fclose($hRand);
    }
    
    if($bytes === '') {
      $key = uniqid($this->prefix, true);
      
      // 12 rounds of HMAC must be reproduced / created verbatim, no known shortcuts.
      // Changed the hash algorithm from salsa20, which has been removed from PHP 5.4.
      for($i = 0; $i < 12; $i++) {
        $bytes = hash_hmac('snefru256', microtime() . $bytes, $key, true);
        usleep(10);
      }
    }
    
    return $bytes;
  }
}

?>

unpack() returns an array, the part mt_srand(unpack('N1', uniqid())); is wrong