Crypto入门 （十一）easychallenge

前言：

　　这题跟python有关，可见看懂python代码还是很有必要得，需要有一些python基础才好

easychallenge：

　题目： 下载后来发现是一个.pyc为后缀得文件，查找资料可知，该文件为python编译后得文件，所以我们第一步应该是反编译，将其转成py文件

我们使用python得uncompyle6库来进行反编译，安装出错或者太慢试试这个，

 pip install -i https://pypi.doubanio.com/simple/ 包名

下面给出如何使用得命令

uncompyle6  -o  F:\桌面\  F:\桌面\tmp\1.pyc

然后将反编译后得py文件内容给出：

 1 # uncompyle6 version 3.7.3
 2 # Python bytecode 2.7 (62211)
 3 # Decompiled from: Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)]
 4 # Embedded file name: ans.py
 5 # Compiled at: 2018-08-09 11:29:44
 6 import base64
 7
 8 def encode1(ans):
 9     s = ''
10     for i in ans:
11         x = ord(i) ^ 36
12         x = x + 25
13         s += chr(x)
14
15     return s
16
17
18 def encode2(ans):
19     s = ''
20     for i in ans:
21         x = ord(i) + 36
22         x = x ^ 36
23         s += chr(x)
24
25     return s
26
27
28 def encode3(ans):
29     return base64.b32encode(ans)
30
31
32 flag = ' '
33 print 'Please Input your flag:'
34 flag = raw_input()
35 final = 'UC7KOWVXWVNKNIC2XCXKHKK2W5NLBKNOUOSK3LNNVWW3E==='
36 if encode3(encode2(encode1(flag))) == final:
37     print 'correct'
38 else:
39     print 'wrong'

可以看到通过该py文件加密后得final是 UC7KOWVXWVNKNIC2XCXKHKK2W5NLBKNOUOSK3LNNVWW3E===  ，然后我们修改一下encode3 encode2 encode1，将其改成decode1 decode2 decode3,

下面给出代码：

 1 # uncompyle6 version 3.7.3
 2 # Python bytecode 2.7 (62211)
 3 # Decompiled from: Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)]
 4 # Embedded file name: ans.py
 5 # Compiled at: 2018-08-09 11:29:44
 6 import base64
 7
 8 def decode3(ans):
 9     s = ''
10     for i in ans:
11 #        x = ord(i) ^ 36
12 #        x = x + 25
13
14         x = ord(i) -25
15         x = x ^ 36
16         s += chr(x)
17
18     return s
19
20
21 def decode2(ans):
22     s = ''
23     for i in ans:
24 #        x = ord(i) + 36
25 #        x = x ^ 36
26
27         x = i ^ 36
28         x = x - 36
29         s += chr(x)
30
31     return s
32
33
34 def decode1(ans):
35     return base64.b32decode(ans)
36
37
38 final = b'UC7KOWVXWVNKNIC2XCXKHKK2W5NLBKNOUOSK3LNNVWW3E==='
39 print(decode3(decode2(decode1(final))))

反向即可解码

参考链接：

https://www.runoob.com/python3/python3-func-ord.html