CTF Broadcast

古城微笑少年丶 2022-12-10 11:26 170阅读 0赞

**题目来源：** 2019\_Redhat

**题目描述：** 粗心的Alice在制作密码的时候，把明文留下来，聪明的你能快速找出来吗？

**题目附件：** 附件1

**1、 附件1**  
![在这里插入图片描述][20200925233132923.png_pic_center]  
**2、解压后**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center]  
**3、选中“task.py”—>打开**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center 1]  
**4、可直接找到flag**

\#!/usr/bin/env python3  
from Crypto.Util import number  
from Crypto.PublicKey import RSA  
from hashlib import sha256  
import json

\#from secret import msg  
msg = ‘Hahaha, Hastad’s method don’t work on this. Flag is flag\{fa0f8335-ae80-448e-a329-6fb69048aae4\}.’  
assert len(msg) == 95

Usernames = \[‘Alice’, ‘Bob’, ‘Carol’, ‘Dan’, ‘Erin’\]  
N = \[ ( number.getPrime(1024) \* number.getPrime(1024) ) for \_ in range(4) \]  
PKs = \[ RSA.construct( (N\[0\], 3) ), RSA.construct( (N\[1\], 3) ), RSA.construct( (N\[2\], 5) ), RSA.construct( (N\[3\], 5) ) \]

for i in range(4):  
name = Usernames\[i+1\]  
open(name+‘Public.pem’, ‘wb’).write( PKs\[i\].exportKey(‘PEM’) )

data = \{‘from’: sha256( b’Alice’ ).hexdigest(),  
‘to’ : sha256( name.encode() ).hexdigest(),  
‘msg’ : msg  
\}  
data = json.dumps(data, sort\_keys=True)  
m = number.bytes\_to\_long( data.encode() )

cipher = pow(m, PKs\[i\].e, PKs\[i\].n)

open(name+‘Cipher.enc’, ‘wb’).write( number.long\_to\_bytes(cipher) )

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center 2]  
**5、OK**

flag\{fa0f8335-ae80-448e-a329-6fb69048aae4\}

[20200925233132923.png_pic_center]: /images/20221123/26ebadcf0ea94834bd507f00b2ddf2cd.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/9205f9b04f6740b7adf126c516771988.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221123/e4ff589ceaa04de8817910335b6eea88.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hZRDY5Ng_size_16_color_FFFFFF_t_70_pic_center 2]: /images/20221123/cea054d3ede44852b5f27bd77a89f569.png