* The path to solution lies in thinking about the `plaintext xor IV` before the AES encryption process .* We had to manage to somehow get the `set of same bytes` that were going to be encrypted as of `'cashcashcashcash' xor IV` . We can feed the appropriate `IV` to the program in order to do so .* Our IV that we will send would be `'flagflagflagflag' xor 'cashcashcashcash' xor IV` so that when we send message as `'flagflagflagflag'` , we can still get the same hash as in message` 'cashcashcashcash'` .