STACK the Flags CTF Write-up — Can COVid steal Bob’s idea?


STACK the Flags was a CTF organised by GovTech’s Cyber Security Group (CSG) over the weekend from 4th — 6th of December. I took part in this CTF in hope to hone my skills in various aspects of cyber security and the challenges in this CTF were certainly insightful. My team and I have definitely learnt a lot from this CTF. Here is the write-up for the cryptography challenge to give you some insights of this challenge and hopefully allow you to take away some knowledge regarding cryptography. Let’s get started!

Initial message exchange between Bob and Alice
Stream 0 containing Bob’s initial request for a keystream generator design and values used in Diffie-Hellman key exchange
FTP File Transfer Traffic
FTP File Transfer Traffic
Stream 1 displaying the FTP Traffic for file transfer between Bob and Alice
zip file transferred in ASCII format
zip file transferred in ASCII format
Stream 2 containing the contents of zip file, screenshot above shows the contents in ASCII format


Since the challenge is titled as Can COVid steal Bob’s idea?, the flag obtained for this challenge is:


Enjoys tinkering with new technologies, spends her free time taking part in CTFs and developing new applications