I just got back from an exam review and there was a question I remembered that I apparently got wrong. I wonder if someone could help me with this, since it bothers me.
The question was something like that:
Between a client and server, a symmetric encryption algorithm is used for the communication. The encrypted data is then hashed with SHA-512 and added to the data stream. Would a man-in-the-middle be able to meddle with the message in a way, the software would not be able to identify the manipulation? It's important that the attacker does not need to get access to the content of the message or manipulate it in a meaningful way. Just the general possibility.
In my answer, I said that, yes, it was possible, but got 0 points on my explanation. I would be interested in the correct answer to that question, out of sheer interest.