题目链接:https://adworld.xctf.org.cn/task/task_list?type=misc&number=1&grade=1&page=5
得到一个图片
用ps录制发现颜色规律
得到如图所示
首先解析gif图片分离成单帧模式
#! /usr/bin/env python2
# -*- coding: utf-8 -*-
import os
from PIL import Image
def main(gif_file):
png_dir = 'frame/'
img = Image.open(gif_file)
try:
while True:
current = img.tell()
img.save(png_dir + str(current + 1) + '.png')
img.seek(current + 1)
except:
pass
if __name__ == '__main__':
gif_file = 'out.gif'
main(gif_file)
得到frame文件夹
然后读取每个png中的对应点的信息,并按照8bit转换为ascii
#! /usr/bin/env python2
# -*- coding: utf-8 -*-
import os
from PIL import Image
def main():
png_dir = 'frame/'
ret = ""
for i in range(0,24):
line = ""
for j in range(0,24):
file_name = "frame/" + str(i * 24 + j + 1) + ".png"
x = j * 10 + 5
y = i * 10 + 5
img = Image.open(file_name)
img = img.convert("RGB")
img_array = img.load()
r, g, b = p = img_array[x, y]
if g == 255:
line += "0"
if r == 255 and b == 255:
line += "1"
if len(line) == 8:
ret += chr(int(line, 2))
line = ""
print(ret)
if __name__ == '__main__':
main()
运行脚本得到
得到:o8DlxK+H8wsiXe/ERFpAMaBPiIcj1sHyGOMmQDkK+uXsVZgre5DSXw==
foremost out.gif
得到密钥: ctfer2333
在线解密网址:http://tool.chacuo.net/cryptdes
得到flag:flag{2ce3b416457d4380dc9a6149858f71db}