can anyone please tell me the difference between unconditionally secure, perfect confidentiality and semantically secure? I know that for perfect confidentiality, we have an adversary A that has an advantage that equals to 0,Pr(w0) = Pr(w1), while the adversary has unlimited resources, and for semantically secure the advantage is equal to 0 but with a negligible epsilon , and i think unconditionally secure means the same thing as semantically secure but the adversary has limited resources? please let me know of the correct difference, thank you.
in the lecture provided by the professor, they are the following definitions:
The concept of perfect privacy is based on the assumption that an attacker observes a unique ciphertext that matches a unique encryption key. We are talking about single-use keys. Nevertheless, we will grant the opponent unlimited computing power.
We will have perfect confidentiality if the opponent (A) fails and succeeds in this game with exactly the same probability, that is to say, $\Pr (W_0) = \Pr (W_1)$.
If so, $A$'s advantage in this game is $AvCP (A, E) = 0$.
We see that it is zero against an unconditionally secure encryption system, even when $A$ has a unlimited amount of resources and unlimited computing time.
and the definition of semantically secure:
where AVss is the advantage of the opponent (which is an efficient opponent meaning the resources are LIMITED)
he also said that:
unconditional security where the adversary would be endowed with infinite computing power.
but at the same time he mentioned that unconditionally secure is equal to semantically secure :
An unconditionally secure encryption system is semantically secure.
Indeed, we have seen that the advantage to an adversary (effective or not) against such encryption is zero.
The disposable mask is a concrete example of an encryption system semantically safe (since unconditionally safe).
so I'm very confused since he said previously that in semantically secure the resources are limited, but in unconditionally secure they aren't limited, yet he said that unconditionally secure is equal to semantically secure??
