This 100pts reverse challenge from 9477 cft ruined my day. I thought it was a very tough reverse engineering challenge. However, it turned out to be a very easy one. My difficult was due to some unintentional problem of the challenge binary.
picoCTF is a computer security game targeted at middle and high school students. Never mind, I'm not a high school student, but I still did this ctf with my friends just for fun. Most of the challenges were straightforward except the last level ones. This ctf was designed for learning so that there was a hint for each challenge. I did four of them, three binary exploit (Nevernote, CrudeCrypt, Fancy Cache) and one reverse engineering (Baleful).
In September 2014, Quarkslab launched a Python challenge. I like pretty much python so I tried it. The challenge had two steps, a highly nested python lambda function and a custom python interpreter." By reversing the lambda function, I got the link for downloading the custom python interpreter. The second step is more interesting that required to reverse the obfuscated python opcodes.I learned much about python internals.
SSTIC is a famous French security conference. Each year the organizer proposes a security challenge for anyone who is interested on security. This year it was a reverse engineering task. The goal of this challenge was to find an email address such as ... @ challenge.sstic.org from a USB trace. I've spent almost two weeks on this challenge. Learned so many things: ADB (USB) forensics, ARM64 instruction set, another VM reverse engineering, Intel Hex, embedded system exploit.