PHPカスタム関数による文字列暗号解読

//  

function string2secret($str)

{

 $key = "123";

 $td = mcrypt_module_open(MCRYPT_DES,'','ecb','');

 $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);

 $ks = mcrypt_enc_get_key_size($td);

 $key = substr(md5($key), 0, $ks);

 mcrypt_generic_init($td, $key, $iv);

 $secret = mcrypt_generic($td, $str);

 mcrypt_generic_deinit($td);

 mcrypt_module_close($td);

 return $secret;

}

//  

function secret2string($sec)

{

 $key = "123";

 $td = mcrypt_module_open(MCRYPT_DES,'','ecb','');

 $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);

 $ks = mcrypt_enc_get_key_size($td);

 $key = substr(md5($key), 0, $ks);

 mcrypt_generic_init($td, $key, $iv);

 $string = mdecrypt_generic($td, $sec);

 mcrypt_generic_deinit($td);

 mcrypt_module_close($td);

 return trim($string);

}

echo secret2string(string2secret("11111111111111111"));

//     11111111111111111

echo '
'.string2secret("11111111111111111");

//    

echo '
';

//$string:        $isEncrypt=true:   $isEncrypt=false:  

function dencrypt($string, $isEncrypt = true, $key = "KEY_SPACE") {

 if (!isset($string{0}) || !isset($key{0})) {

  return false;

 }

 $dynKey = $isEncrypt ? hash('sha1', microtime(true)) : substr($string, 0, 40);

 $fixedKey = hash('sha1', $key);

 $dynKeyPart1 = substr($dynKey, 0, 20);

 $dynKeyPart2 = substr($dynKey, 20);

 $fixedKeyPart1 = substr($fixedKey, 0, 20);

 $fixedKeyPart2 = substr($fixedKey, 20);

 $key = hash('sha1', $dynKeyPart1 . $fixedKeyPart1 . $dynKeyPart2 . $fixedKeyPart2);

 $string = $isEncrypt ? $fixedKeyPart1 . $string . $dynKeyPart2 : (isset($string{339}) ? gzuncompress(base64_decode(substr($string, 40))) : base64_decode(substr($string, 40)));

 $n = 0;

 $result = '';

 $len = strlen($string);

 for ($n = 0; $n < $len; $n++) {

  $result .= chr(ord($string{$n}) ^ ord($key{$n % 40}));

 }

 return $isEncrypt ? $dynKey . str_replace('=', '', base64_encode($n > 299 ? gzcompress($result) : $result)) : substr($result, 20, -20);

}

echo strlen(dencrypt("12345678912345"));