BugKu-CTF(解密篇Crypto)--where is flag 5

Gx8EAA8SCBIfHQARCxMUHwsAHRwRHh8BEQwaFBQfGwMYCBYRHx4SBRQdGR8HAQ0QFQ==
 
得到一串密文，一看就是base64，但是工具解不出来，用python是可以的
 
 

import base64
str = "Gx8EAA8SCBIfHQARCxMUHwsAHRwRHh8BEQwaFBQfGwMYCBYRHx4SBRQdGR8HAQ0QFQ=="
str =base64.b64decode(str)
print(str)

 得到一串看似十六进制的内容
b'\x1b\x1f\x04\x00\x0f\x12\x08\x12\x1f\x1d\x00\x11\x0b\x13\x14\x1f\x0b\x00\x1d\x1c\x11\x1e\x1f\x01\x11\x0c\x1a\x14\x14\x1f\x1b\x03\x18\x08\x16\x11\x1f\x1e\x12\x05\x14\x1d\x19\x1f\x07\x01\r\x10\x15'
 
 
把x去掉（丢word里替换一下，比写脚本快）
 
1b 1f 04 00 0f 12 08 12 1f 1d 00 11 0b 13 14 1f 0b 00 1d 1c 11 1e 1f 01 11 0c 1a 14 14 1f 1b 03 18 08 16 11 1f 1e 12 05 14 1d 19 1f 07 01 10 15
 
b、f不属于ascii码里的东西、字母前面只有1、0提取出来
110001011101011100111110101111101011111011110011
转ascii码 七位转一个
b u g k u { c
 
 

import base64
str = "Gx8EAA8SCBIfHQARCxMUHwsAHRwRHh8BEQwaFBQfGwMYCBYRHx4SBRQdGR8HAQ0QFQ=="
str = base64.b64decode(str)
l = [bin(i).replace("0b", "") for i in str]
print(l)

补全0
import base64
str = "Gx8EAA8SCBIfHQARCxMUHwsAHRwRHh8BEQwaFBQfGwMYCBYRHx4SBRQdGR8HAQ0QFQ=="
str = base64.b64decode(str)
l = [bin(i).replace("0b", "") for i in str]
l = ["0"*(5-len(i))+i if(len(i) != 5) else i for i in l]
print(l)

借鉴肖萧然大佬的博客
import base64
str = "Gx8EAA8SCBIfHQARCxMUHwsAHRwRHh8BEQwaFBQfGwMYCBYRHx4SBRQdGR8HAQ0QFQ=="
str = base64.b64decode(str)
l = [bin(i).replace("0b", "") for i in str]
l = ["0"*(5-len(i))+i if(len(i) != 5) else i for i in l]
 
for i in range(5):
    str = "".join([ii[i] for ii in l])
    print(*[chr(int(str[i:i+7], 2)) for i in range(0, len(str), 7)], sep="", end="")

bugku{ce26f61d40fea75fc0b980d7588e}