Fidget-Cube's Security Blog
I like puzzles
Fidget-Cube's Security Blog
I like puzzles
He did it! He said the line!
(this is not a serious blog post if you couldn’t tell, adult language ahead)
JavaScriptJust this past weekend, Pacific Hacker's Association and HackMiami joined forces to compete in the DEFCON CTF Qualifiers. The top 12 teams from this CTF go on to play the most competitive and challenging CTF in the world at DEFCON 31. Though, to be fair, our team wasn't of that caliber. We were able to solve 2 challenges (not counting the sanity checks) and finished in 92nd place, which is a great success by my standards! I was able to solve this one with the help of my friend Sam. It's a reverse engineering challenge, but with Python code instead of x86 assembly, which makes things much nicer.
Reverse EngineeringThis server is basically a simulation of the IND-CCA2 game testing a custom cryptographic system. The game is described in detail here https://en.wikipedia.org/wiki/Ciphertext_indistinguishability.
The server makes 128 passes, generating a random bit (0 or 1) each pass. Our goal is to call a "Solve" function, and correctly "guess" the bit 128 times, at which point a flag is printed. In addition, the server also provides "Query Encryption" and "Query Decryption" functions.
Cryptography