Foreword I participated in Insomni’hack 23 with NUS Greyhats. We managed to get 12th place. I was in the Lunar New Year celebration mode and basically got carried by the team. I only look at one challenge in the Forensics category. I did not manage to solve it, but I will document (briefly) how we do to obtain the solution. Challenges Autopsy Big kudos to IDissEverything of NUS Greyhats for solving this.

Foreword My first non-NUS CTF! I was mostly carried by the insane people @ NUS Greyhats. Quals I did manage to contribute something though, the Welcome challenge (which is to find the flag hidden in the emotes on the ISITDTU CTF Discord server), a OSINT and Misc challenge. Find A tough OSINT challenge. Initially we are only given the following image. There was initially no clues given by the challenge organizer.

Foreword Second CTF from NUS Greyhats. Initially I do not have any intention of writing writeups as the time for the CTF is only a day, so the following writeups are based on my recollection of the event. The web challenges done are gone, as there is no file stored. Challenges AmongUs This is a challenge involving image steganography. Not so difficult if you know the proper tooling for the challenge.

Foreword First ever CTF. Managed to solve a few challenges and learnt a ton! Challenges Baby The message is encrypted using the textbook RSA algorithm, and to decrypt the message we need to retrieve the values of the two primes p and q. We know the value of $r \times p - s \times q$, let the value be a. We have this observation that $r > s$, and $a < 0$, hence $p < q$.