PHP で DES 暗号化と復号化を実装する簡単な方法

function des_encrypt($str, $key) {
  $block = mcrypt_get_block_size('des', 'ecb');
  $pad = $block - (strlen($str) % $block);
  $str .= str_repeat(chr($pad), $pad);
  return mcrypt_encrypt(MCRYPT_DES, $key, $str, MCRYPT_MODE_ECB);
}

function des_decrypt($str, $key) {
  $str = mcrypt_decrypt(MCRYPT_DES, $key, $str, MCRYPT_MODE_ECB);
  $len = strlen($str);
  $block = mcrypt_get_block_size('des', 'ecb');
  $pad = ord($str[$len - 1]);
  return substr($str, 0, $len - $pad);
}