HackIM Postmortem: So HackIM is over. Hopefully some of you participated and had some fun. There were some issues with this CTF regarding question quality/difficulty, so if this was your first CTF, dont think of this one as a representation of all CTFs, there are much better ones where youll solve more problems and still learn a lot. That being said, Id like to use this group to discuss problems and anything we learned that could help other people. My team solved Programming 1 and 2, Crypto 1 and 3, Forensics 1, 3, and 4, Trivia 2 and 4, and Web 1, 2, 3, 4, and 5. If you have questions on any of those let me know and post whatever you solved. If you find writeups, you can post them as a comment. As for things I learned: - Peepdf is a really cool tool for analyzing PDF files - pwntools is awesome - The python requests library is awesome - The PIL image library is awesome (I actually already knew that) - pytesseract is a cool library for doing OCR stuff with Python, but it turns out its not hard to roll your own captcha solver if the letters used are in the same location every time with no distortion :) - `from collections import Counter` - Why has no one told me about this? - Even if you understand length extension attack really well, dont implement them yourself. Just use Hashpump. - How to group a randomly generated files in a randomly generated file directory structure by type (invaluable for forensics problems): `find . -type f -exec file {} \; | rev | sort | rev | less` - Rabins cryptosystem is really interesting. Learned the chinese remainder theorem and the extended euclidean algorithm in order to decrypt it. Also, msieve is a great tool for factoring prime numbers. - ALWAYS join the competition IRC channel. Even when/if you go to bed, make sure your client is connected and read the messages you missed in the morning. - Recruit an ACM world finalist on your CTF team. It really helps with programming challenges :) Anything else people want to add?
Posted on: Sun, 11 Jan 2015 21:06:51 +0000
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