攻防世界MISC_base64stego

环境

题目下载，zip伪加密，base64隐写

flag{Base_sixty_four_point_five}

wp

zip伪加密，修改标志位为0

解压出一个文本文件，里面是多行的base64，考虑base64隐写

ptyhon

# -*- coding: utf-8 -*-
import base64
b64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
with open('D:\\rainbow\\Downloads\\a2eb7ceaf5ab49f7acb33de2e7eed74a\\stego.txt', 'rb') as f:
    bin_str = ''
    for line in f.readlines():
        stegb64 = str(line, "utf-8").strip("\r\n")
        rowb64 = str(base64.b64encode(base64.b64decode(stegb64)), "utf-8").strip("\r\n")
        equalnum = stegb64.count('=')
        if equalnum:
            offset = abs(b64chars.index(stegb64.replace('=','')[-1])-b64chars.index(rowb64.replace('=','')[-1]))
            bin_str += bin(offset)[2:].zfill(equalnum * 2)
        print(''.join([chr(int(bin_str[i:i + 8], 2)) for i in range(0, len(bin_str), 8)]))