I have one question that I couldn't come up with a nice solution.
So let's have this analogy, I have a box full of money and I want to deliver to this my friend. Here if we think of a potential attacker there are two possible ways, first the attacker would be between us , so called postman or he could pretend like he is the recipient.
This being the case, what are the properties of both type of attackers?
For the first attacker in the role of the postman, he could simply observe, modify or block the delivery of the box(message in cryptography). And my question here is what could he do if he disguises as a receiver unlik the postman attacker?
and what other kind of attacks could these both attacker types do?