xxtea暗号解読アルゴリズムのPHP実現

    Class Xxtea {  
        public function encrypt($s, $key) {  
            return base64_encode(self :: xxtea_encrypt($s, $key));  
        }  
        public function decrypt($e, $key) {  
            return self :: xxtea_decrypt(base64_decode($e), $key);  
        }  
        private function long2str($v, $w) {  
            $len = count($v);  
            $n = ($len -1) << 2;  
            if ($w) {  
                $m = $v[$len -1];  
                if (($m < $n -3) || ($m > $n))  
                    return false;  
                $n = $m;  
            }  
            $s = array ();  
            for ($i = 0; $i < $len; $i++) {  
                $s[$i] = pack("V", $v[$i]);  
            }  
            if ($w) {  
                return substr(join('', $s), 0, $n);  
            } else {  
                return join('', $s);  
            }  
        }  
        private function str2long($s, $w) {  
            $v = unpack("V*", $s . str_repeat("\0", (4 - strlen($s) % 4) & 3));  
            $v = array_values($v);  
            if ($w) {  
                $v[count($v)] = strlen($s);  
            }  
            return $v;  
        }  
        private function int32($n) {  
            while ($n >= 2147483648)  
                $n -= 4294967296;  
            while ($n <= -2147483649)  
                $n += 4294967296;  
            return (int) $n;  
        }  
        private function xxtea_encrypt($str, $key) {  
            if ($str == "") {  
                return "";  
            }  
            $v = self :: str2long($str, true);  
            $k = self :: str2long($key, false);  
            if (count($k) < 4) {  
                for ($i = count($k); $i < 4; $i++) {  
                    $k[$i] = 0;  
                }  
            }  
            $n = count($v) - 1;  
            $z = $v[$n];  
            $y = $v[0];  
            $delta = 0x9E3779B9;  
            $q = floor(6 + 52 / ($n +1));  
            $sum = 0;  
      
            while (0 < $q--) {  
                $sum = self :: int32($sum + $delta);  
                $e = $sum >> 2 & 3;  
                for ($p = 0; $p < $n; $p++) {  
                    $y = $v[$p +1];  
                    $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                    $z = $v[$p] = self :: int32($v[$p] + $mx);  
                }  
                $y = $v[0];  
                $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                $z = $v[$n] = self :: int32($v[$n] + $mx);  
            }  
            return self :: long2str($v, false);  
        }  
        private function xxtea_decrypt($str, $key) {  
            if ($str == "") {  
                return "";  
            }  
            $v = self :: str2long($str, false);  
            $k = self :: str2long($key, false);  
            if (count($k) < 4) {  
                for ($i = count($k); $i < 4; $i++) {  
                    $k[$i] = 0;  
                }  
            }  
            $n = count($v) - 1;  
      
            $z = $v[$n];  
            $y = $v[0];  
            $delta = 0x9E3779B9;  
            $q = floor(6 + 52 / ($n +1));  
            $sum = self :: int32($q * $delta);  
      
            while ($sum != 0) {  
                $e = $sum >> 2 & 3;  
                for ($p = $n; $p > 0; $p--) {  
                    $z = $v[$p -1];  
                    $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                    $y = $v[$p] = self :: int32($v[$p] - $mx);  
                }  
                $z = $v[$n];  
                $mx = self :: int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self :: int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
                $y = $v[0] = self :: int32($v[0] - $mx);  
                $sum = self :: int32($sum - $delta);  
            }  
            return self :: long2str($v, true);  
        }  
    }  

 
説明:
encrypt(明文文字列、鍵文字列);