我们如何在PHP中创建一个相当安全的密码哈希？

几个指针：

>不要对所有密码使用单一盐.每个密码使用随机生成的盐.
>不要重新创建一个未修改的哈希(碰撞问题,see my previous answer,您需要无限量的哈希输入).
>不要尝试创建自己的哈希算法或混合匹配算法到复杂的操作.
>如果卡住了破碎/不安全/快速哈希原语,请使用key strengthening.这样可以增加攻击者计算彩虹表所需的时间.例：

function strong_hash($input,$salt = null,$algo = 'sha512',$rounds = 20000) {
  if($salt === null) {
    $salt = crypto_random_bytes(16);
  } else {
    $salt = pack('H*',substr($salt,32));
  }

  $hash = hash($algo,$salt . $input);

  for($i = 0; $i < $rounds; $i++) {
    // $input is appended to $hash in order to create
    // infinite input.
    $hash = hash($algo,$hash . $input);
  }

  // Return salt and hash. To verify,simply
  // passed stored hash as second parameter.
  return bin2hex($salt) . $hash;
}

function crypto_random_bytes($count) {
  static $randomState = null;

  $bytes = '';

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

  if($bytes === '' && is_readable('/dev/urandom') &&
     ($hRand = @fopen('/dev/urandom','rb')) !== FALSE) {
    $bytes = fread($hRand,$count);
    fclose($hRand);
  }

  if(strlen($bytes) < $count) {
    $bytes = '';

    if($randomState === null) {
      $randomState = microtime();
      if(function_exists('getmypid')) {
        $randomState .= getmypid();
      }
    }

    for($i = 0; $i < $count; $i += 16) {
      $randomState = md5(microtime() . $randomState);

      if (PHP_VERSION >= '5') {
        $bytes .= md5($randomState,true);
      } else {
        $bytes .= pack('H*',md5($randomState));
      }
    }

    $bytes = substr($bytes,$count);
  }

  return $bytes;
}

而不是部署自己的(固有的缺陷)哈希/盐算法,为什么不使用由安全专业人士开发的？

使用bcrypt.这是为了这一点而开发的.缓慢和多轮确保攻击者必须部署大量资金和硬件才能破解您的密码.添加到每个密码盐(bcrypt REQUIRES盐),你可以确定攻击几乎是不可行的,没有可笑的资金或硬件.

Portable PHP Hashing Framework在非便携式模式下,您可以轻松地使用bcrypt生成散列.

您还可以使用crypt()函数生成输入字符串的bcrypt哈希值.如果你沿着这条路线走下去,确保每个哈希生成一个盐.

此类可以自动生成盐并根据输入验证现有散列.

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

    $this->rounds = $rounds;
  }

  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() {
    $salt = sprintf('$2a$%02d$',$this->rounds);

    $bytes = $this->getRandomBytes(16);

    $salt .= $this->encodeBytes($bytes);

    return $salt;
  }

  private $randomState;
  private function getRandomBytes($count) {
    $bytes = '';

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

    if($bytes === '' && is_readable('/dev/urandom') &&
       ($hRand = @fopen('/dev/urandom','rb')) !== FALSE) {
      $bytes = fread($hRand,$count);
      fclose($hRand);
    }

    if(strlen($bytes) < $count) {
      $bytes = '';

      if($this->randomState === null) {
        $this->randomState = microtime();
        if(function_exists('getmypid')) {
          $this->randomState .= getmypid();
        }
      }

      for($i = 0; $i < $count; $i += 16) {
        $this->randomState = md5(microtime() . $this->randomState);

        if (PHP_VERSION >= '5') {
          $bytes .= md5($this->randomState,true);
        } else {
          $bytes .= pack('H*',md5($this->randomState));
        }
      }

      $bytes = substr($bytes,$count);
    }

    return $bytes;
  }

  private function encodeBytes($input) {
    return strtr(rtrim(base64_encode($input),'='),'+','.');
  }
}

您可以使用此代码：

$bcrypt = new Bcrypt(15);

$hash = $bcrypt->hash('password');
$isGood = $bcrypt->verify('password',$hash);