[ACTF新生赛2020]crypto-des-优快云博客

本文链接：https://blog.youkuaiyun.com/m0_52727862/article/details/119304431

本文介绍了ACTF新生赛2020中的一道crypto-des题目，提供了加密的key和hint，解密脚本用于获取解密zip的key。解密过程涉及DES加密，通过给定的16轮子密钥进行base64解码和decrypt()函数解密。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

[ACTF新生赛2020]crypto-des

附件：

$[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-CA9Zv3pL-1627826226283)(C:\Users\86183\Desktop\ZERO\2ero\WP\BUUCTF\Crypto[ACTF新生赛2020]crypto-des\image-20210731144925508.png)]$

加密的 easydes.zip ，通过解密encryptedkey.txt以获取解密 zip 的 key

encryptedkey.txt:

72143238992041641000000.000000,
77135357178006504000000000000000.000000,
1125868345616435400000000.000000,
67378029765916820000000.000000,
75553486092184703000000000000.000000,
4397611913739958700000.000000,
76209378028621039000000000000000.000000

hint.txt:

To solve the key, Maybe you know some interesting data format about C language?

压缩包尝试爆破并没有结果。。。。。

解密脚本：

import struct

s = [72143238992041641000000.000000,77135357178006504000000000000000.000000,1125868345616435400000000.000000,67378029765916820000000.000000,75553486092184703000000000000.000000,4397611913739958700000.000000,76209378028621039000000000000000.000000]
a = ''
b = ''
for i in s:
    i = float(i)
    a += struct.pack('<f',i).hex()        #小端
print(a)

for j in s:
    i = float(i)
    b += struct.pack('>f',i).hex()        #小端
print(b)

# -*- coding: utf-8 -*-
import binascii
#16进制整数转ASCii编码字符串
a = 0x496e74657265737472696e67204964656120746f20656e6372797074
a1 = hex(a) #转换成相同的字符串即'0x665554'
a2 = a1[2:] #截取掉'0x'
a3 = binascii.a2b_hex(a2) #转换成ASCii编码的字符串
print(a3)

b = 0x74707972747079727470797274707972747079727470797274707972
b1 = hex(b) #转换成相同的字符串即'0x665554'
b2 = b1[2:] #截取掉'0x'
b3 = binascii.a2b_hex(b2) #转换成ASCii编码的字符串
print(b3)

运行得到：

496e74657265737472696e67204964656120746f20656e6372797074
74707972747079727470797274707972747079727470797274707972
b'Interestring Idea to encrypt'
b'tpyrtpyrtpyrtpyrtpyrtpyrtpyr'

解得key：

Interestring Idea to encrypt

解压得到加密脚本：

import pyDes
import base64
from FLAG import flag
deskey = "********"
DES = pyDes.des(deskey)
DES.setMode('ECB')
DES.Kn = [
			[1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0],
			[1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0], 
			[0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0],
			[1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1], 
			[0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1