I have been reading to understand the need to randomise the IV but have failed to understand this yet.
Could someone please explain why do we need to randomise the IV if we somehow need to send the IV with the cipher text because the receiver, even though has the key would not know the random IV.
Therefore, wouldn't an adversary who has access to the cipher text can see the random IV for each message?
Why isn't it better to agree on a fixed IV like the key and not send it over with the cipher text?