0x41414141 CTF: Register Secret PIN

This is from the 0x41414141 CTF.

When I went to register to compete in the 0x41414141 CTF I found that is was a little different from other CTFd based CTFs. Besides the normal registration information, it asks for a pin code (secret pin code for CTF registration).

Going back and looking through the site, I see on the About page that the secret pin code for CTF entry is hidden somewhere on the site:

After pouring through the source files for each page on the site, running curl POSTs, and looking at previous versions of the site on Archive.org, I considered the steganography approach.

Besides the normal social media link images, there are only two images on the site. One is the animated Offshift logo, which yielded no obvious results when running strings, binwalk, or other stego decoders:

The second image is a small Offshift logo that is used as the header logo:

After downloading this image, I ran strings on it to look for anything interesting:

Ahh! I see “secret: 100100100101” at the bottom of the results.

I convert the binary string to decimal:

echo "obase=10; ibase=2; 100100100101" | bc

Using the resulting decimal value as the pin, I am now able to register for the CTF.

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