看雪2019晋级赛

题目一 签到题目 流浪者

这道题目直接测试，下断点。

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#-*-coding:utf-8 -*-

print "Start... ..."
cin = "KanXueCTF2019JustForhappy"
flag = ""
for i in cin:
	if i>= 'o' and i <= 'z':
		sub = ord('o')-ord('C')
		c = chr(ord(i) - sub)
		flag = flag +c
	elif i >= 'O' and i <= 'Z':
		c = i
		flag = flag + c
	elif i >='B' and i<= 'N':
		sub = ord('a') - ord('B')
		c = chr(ord(i) + sub)
		flag = flag + c
	elif i>='j' and i  <='n':
		sub = ord('n') - ord ('j')
		c = chr(ord(i)+ sub)
		flag = flag + c
	elif i>='0' and i <='7':
		sub = ord('s')-ord('0')
		c = chr(ord(i)+sub)
		flag = flag + c
	elif i>='8' and i <='9':
		sub = ord('A')-ord('8')
		c = chr(ord(i)+ sub)
		flag = flag + c
	elif i>='a' and i<='i':
		sub = ord('a')-ord('0')
		c = chr(ord(i)-sub)
		flag = flag +c
	elif i=='A':
		c='9'
		flag=flag +c
print flag
print "End... ..."

"""
j012AB
Kabc89
CDEFGHIJKLMN OPQRSTUVWXYZ
opqrstuvwxyz OPQRSTUVWXYZ


abcdefghijklm nopqr stuvwxyzAB
BCDEFGHIJKLMN jklmn 0123456789

0123456789
abcdefghiA

"""

题目十 初入好望角

是.net加密的，C#题目。 AES加密,附上python 和 C#两套解密脚本

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from Crypto.Cipher import AES
from binascii import b2a_hex, a2b_hex

import base64
# 如果text不足16位的倍数就用空格补足为16位
def add_to_16(text):
    if len(text.encode('utf-8')) % 16:
        add = 16 - (len(text.encode('utf-8')) % 16)
    else:
        add = 0
    text = text + ('\0' * add)
    return text.encode('utf-8')


# 加密函数
def encrypt(text):
    key = '9999999999999999'.encode('utf-8')
    mode = AES.MODE_CBC
    iv = b'qqqqqqqqqqqqqqqq'
    text = add_to_16(text)
    cryptos = AES.new(key, mode, iv)
    cipher_text = cryptos.encrypt(text)
    # 因为AES加密后的字符串不一定是ascii字符集的，输出保存可能存在问题，所以这里转为16进制字符串
    return b2a_hex(cipher_text)


# 解密后，去掉补足的空格用strip() 去掉
def decrypt(text,key):
    iv = 'Kanxue2019CTF-Q1'.encode('utf-8')
    #key = b'Kanxue2019\0\0\0\0\0\0'
    #6DDEF7A43C004F7D6983044B1E36A93459F18BC837C46EAF321132734163A0B4
    mode = AES.MODE_CBC
    cryptos = AES.new(key, mode, iv)
    plain_text = cryptos.decrypt((text))
    return bytes.decode(plain_text).rstrip('\0')


if __name__ == '__main__':
 
    #print (hex(ord(a[i])))
    encoding="6DDEF7A43C004F7D6983044B1E36A93459F18BC837C46EAF321132734163A0B4"
    key = ""
    for i in range(0,len(encoding),2):
        #print (encoding[i]+encoding[i+1])
        b = ((int)((i)/2))
        #if b < len(a):
        text = "0x"+encoding[i]+encoding[i+1]
        flag = int(text,16)
        key = key + chr(flag)
            #print (chr(flag))
    key=encoding
    key = bytes.fromhex(key)
    print (key)
    e = "4RTlF9Ca2+oqExJwx68FiA=="
    e = base64.b64decode(e)
    s = decrypt(e,key)
    print (s)
"""
python 3.5以后
>>> a = 'aabbccddeeff'
>>> a_bytes = bytes.fromhex(a)
>>> print(a_bytes)
b'\xaa\xbb\xcc\xdd\xee\xff'
>>> aa = a_bytes.hex()
>>> print(aa)
aabbccddeeff
>>>

python2.7
>>> a = 'aabbccddeeff'
>>> a_bytes = a.decode('hex')
>>> print(a_bytes)
b'\xaa\xbb\xcc\xdd\xee\xff'
>>> aa = a_bytes.encode('hex')
>>> print(aa)
aabbccddeeff
>>>

python2.8-python3.5
>>> a = 'aabbccddeeff'
>>> a_bytes = bytes.fromhex(a)
>>> print(a_bytes)
b'\xaa\xbb\xcc\xdd\xee\xff'
>>> aa = ''.join(['%02x' % b for b in a_bytes])
>>> print(aa)
aabbccddeeff
>>>
"""

以下是C#code通过在线运行得到答案

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//Rextester.Program.Main 是代码入口函数，不要改变它.
//编译版本 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;


namespace Rextester
{
    public class Program
    {
		private const string string_0 = "Kanxue2019CTF-Q1";

	private const int int_0 = 256;

        public static void Main(string[] args)
        {
            //你的代码...
            Console.WriteLine("Hello, world!");
					if (Program.smethod_0("hello", "Kanxue2019") == "4RTlF9Ca2+oqExJwx68FiA==")
		{
			Console.WriteLine("Congratulations!  : )");
			Console.ReadLine();
		}
			
				 string flag = Program.decry("4RTlF9Ca2+oqExJwx68FiA==");
			
        }
		
		public static string smethod_0(string string_1, string string_2)
	{
		byte[] bytes = Encoding.UTF8.GetBytes("Kanxue2019CTF-Q1");
		byte[] bytes2 = Encoding.UTF8.GetBytes(string_1);
		byte[] bytes3 = new PasswordDeriveBytes(string_2, null).GetBytes(32);
			byte[] a=new byte[10];

string text = "";
for (int i = 0; i < bytes3.Length; i++)
{
　　text += bytes3[i].ToString("X2") ;
}
			Console.WriteLine(text);
			string str = System.Text.Encoding.Default.GetString ( bytes3 );
			Console.WriteLine(str);

		ICryptoTransform transform = new RijndaelManaged
		{
			Mode = CipherMode.CBC
		}.CreateEncryptor(bytes3, bytes);
		MemoryStream memoryStream = new MemoryStream();
		CryptoStream expr_4F = new CryptoStream(memoryStream, transform, CryptoStreamMode.Write);
		expr_4F.Write(bytes2, 0, bytes2.Length);
		expr_4F.FlushFinalBlock();
		byte[] inArray = memoryStream.ToArray();
		memoryStream.Close();
		expr_4F.Close();
		return Convert.ToBase64String(inArray);
	}


		
	public static string decry(string source){
		//Console.WriteLine("no answer");
	//创建一个MemoryStream实例，存放收到的加密数据字节流
		byte[] encryptoByte = Convert.FromBase64String(source);
		 //byte[] encryptoByte = mStream.ToArray();
 		MemoryStream encryptoStream = new MemoryStream(encryptoByte);
  //创建RijndaelManaged实例
 		RijndaelManaged RMCrypto = new RijndaelManaged();
  
 		byte [] IV = Encoding.UTF8.GetBytes("Kanxue2019CTF-Q1");
		string string_2 = "Kanxue2019";
		Console.WriteLine("no answer");
		byte [] Key =  new PasswordDeriveBytes(string_2, null).GetBytes(32);

 //创建用于解密的CryptoStream实例
		CryptoStream CryptStream = new CryptoStream(encryptoStream,
   		RMCrypto.CreateDecryptor(Key, IV),
   		CryptoStreamMode.Read);

 //创建StreamReader实例，从CryptoStream中读出数据，
 //StreamReader默认使用UTF8编码读出的数据
 		StreamReader SReader = new StreamReader(CryptStream);

//输出解密后的消息.
		Console.WriteLine("The decrypted original message: {0}",SReader.ReadToEnd());
		Console.WriteLine("no answer");
		return SReader.ReadToEnd();

	}
    }
}