In this challenge we are given a very simple python service to connect to. In a loop, it reads some data from the client, appends a flag to it, compresses it, encrypts it with AES in CTR mode, and then returns it to the client. The goal is to find the flag, of course!
One of us devised a new cryptosystem! Can you break it?
For this challenge we had access to a home-grown crypto system, allowing us to encrypt and decrypt messages. However the server refused to decrypt the encrypted flag given.
Let’s see if we can trick it.