Prior to the Neg9 Seattle meeting on 2015-05-26, I issued a challenge to participants:

I have prepared a CTF-like challenge. It is not a pwnable. It’s more like a misc/forensics/programming challenge. I will distribute the file at the meeting and we will split off as groups or individuals to solve it. I have given three hints:

  • It will involve a (well-formed) PNG image

  • It will involve alpha layering

  • It will involve morse code

The purpose of this exercise isn’t to stump everybody with a ultra-hard challenge. It’s to get you thinking about building up your toolkit. With those hints, do you have the necessary tools and libraries to quickly tackle the challenge at hand? Dealing with pulling apart images programmatically is one area that your toolkit may be lacking.

So ponder on the hints, do some research for what would work well with your normal language of choice and workflow, and come to the meeting prepared and ready to solve the challenge efficiently.

The challenge went well and Javantea was the first to solve it in just under an hour. After that, other groups continued to solve it for the duration of the meeting.

Weren’t at the meeting? (why not?) Grab the challenge file here:

The hints given below were revealed slowly as the night went on. They’ve been obfuscated to allow you to work at your own pace with the number of hints that you want.

  • It will involve a (well-formed) PNG image

  • It will involve alpha layering

  • It will involve morse code

  • SW1hZ2UgaGFzIDUyMiByb3dzIG9mIHBpeGVscy4K

  • T2J2aW91cyBmbGFnIGlzIG9idmlvdXMuCg==

  • Tm9uLWFtYmlndW91cyBtb3JzZSBsZXR0ZXIgZGVsaW1pdGluZyBpZiBkb25lIHJpZ2h0Lgo=

  • eCBkb2Vzbid0IG1hdHRlciEgKHdhcyBkZWVtZWQgdG8gYmUgYSBjb25mdXNpbmcgaGludCkK

  • SXQncyBzb2x2YWJsZSEgQXQgbGVhc3QgNiB0aW1lcyEK

  • UGl4ZWxzIHdpdGggQSAhPSAyNTUgYXJlIHNwZWNpYWwuIEFueXRoaW5nIGVsc2Ugc3BlY2lhbCBhYm91dCB0aGVtPwo=


  • Q2FzZSBpbnNlbnNpdGl2ZQo=

  • MTMzNyBtZWFucyBub24tbGV0dGVycyEK

  • V2hhdCBkb2VzIGNvbG9yIGxvb2sgbGlrZT8gV2hhdCBkb2VzIEImVyBsb29rIGxpa2U/Cg==

  • V2lraXBlZGlhIGlzIHlvdXIgZnJpZW5kLgo=