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Magic PNGs

题目

Magic PNGs:

Can you help me open this zip file? I seem to have forgotten its password. I think the image file has something to do with it.

Hint: You may have to hash the secret word to get the flag...

tryme.zip

you_cant_see_me.png

解决方案

下载到一个tryme.zip和一个you_cant_see_me.png,压缩包内含flag.txt但是被加密了;png打不开,还嘲讽我(?),先看一下十六进制:

vim -b you_cant_see_me.png
:%!xxd

然后发现文件头有问题;而且竟然没有IDAT,估计是被破坏了,不过竟然能搜到一个小写的idat,确认过眼神,是应该改的地方。改回来保存看看:

MAGIC_PNGS-1.png

MAGIC_PNGS-2.png

:%!xxd -r
:wq

已经可以预览图片了:

MAGIC_PNGS-3.png

打开:

MAGIC_PNGS-4.png

行吧旋转一下:

MAGIC_PNGS-5.png

懒得写个镜像了,直接拿手机前摄拍了一张就可以看到正的了:

h4CK3RM4n

题目hint表示应该先哈希一下再try一下:

2c919f82ee2ed6985d5c5e275d67e4f8

解压flag.txt成功get到flag:

pctf{y0u_s33_m33_n0w!}

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