实验吧 NSCTF web200

题目链接：http://ctf5.shiyanbar.com/web/web200.jpg

加密

	function encode ($str){
		$_o = strrev($str);							// 反转字符串		
		for ($_0=0;$_O<strlen($_o);$_O++); {		// 所有字符ASCII值+1
			$_c = substr($_o,$_O, 1);
			$__ = ord($_c)+1;
			$_c = chr($__);
			$_  = $_.$_c;
		}
		return str_rot13 (strrev(base64_encode ($_)))	// 最终加密
	}

解密

	$str = "a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
	$_   = "";
	$_o = base64_decode(strrev(str_rot13($str)));	// 初步解密
	for ($_0=0;$_0<strlen($_O);$_O++) 				// 所有字符ASCII值-1
	{		
		$_c = substr($_o,$_O,1);
		$__ = ord($_c)-1;
		$_c = chr($__);
		$_= $_.$_c;
	}
	echo strrev($_);								// 反转字符串
?>

得到flag：flag:{NSCTF_b73d5adfb819c64603d7237fa0d52977}