I recently started doing CTF challenges. A few days ago, I was working on a challenge from 247CTF.com. I found a challenge that, in my opinion, shows why using ECB(Electronic Codebook) mode for encrypting with block ciphers like AES or Twofish isn’t a good idea. So, I decided to write a series of blog posts where I solve these challenges and explain how to prevent these kinds of attacks. The challenge was quite simple. It was a website with two parts: /encrypt and /get_flag. Both parts needed a ...