CBC-Bit-Flipping

Challenge Points: 138 Challenge Description: We’ve developed a new restricted shell. It also allows to manage user access more securely. Let’s try it nc crypto-01.v7frkwrfyhsjtbpfcppnu.ctfz.one 1337 In this post, I will be discussing my solution for USSH-3.0 challenge from CTFZone which I think is the unintended way. The challenge was quite peculiar, involving “blind” exploit as you will see in this write-up. Some parts of the challenge might look like guessing, but if you read this write-up start-to-end, you will see that it was a well-tailored challenge. ...

Challenge Points: 498 Challenge Description: The Dungeon Keeper learned from its mistake. This next lock is protected by even stronger encryption. We’re so close to the final level…there has to be a way in. The Dark Dungeon series of crypto challenges were the only ones I enjoyed solving in the CTF. Rest of the crypto challenges were pathetic, involved a lot of guessing and were not really crypto challenges and can be called as puzzles. ...

In this blog post, the attack on CBC mode of block cipher encryption will be discussed and in the end, detailed writeup for the 16th challenge of Matasano-Crypto-Challenge i.e. about the Bit Flipping Attack in AES-CBC will be provided with explanation! I want the reader to go through these concepts discussed in the following blog posts, before actually understanding how the CBC Bit-Flipping Attack works: Mode Detection Oracle Blocksize Detection Oracle We will list down all the information one must have access to, in order to initiate this attack: ...