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We have a Padding Oracle if there is a different response from the server gives us an indication of the correctness of the pad (say if this needs proving). We can establish this by playing a game where we send badly padded cipher-text and random strings to the server, finally submitting some at random and seeing if we can get a non-negligible Advantage is ...


2

Here's the next step in the iteration, which should be easy to understand: Let's call the oracle on 2P and 4P: Answer (even,even) means, that $P<N/4$ (this is still easy: Otherwise either 2P or 4P would be greater than N). Answer (even,odd) means $N/4<P<N/2$. (odd,even) means $N/2<P<3N/4$ and (odd,odd) means $3/4N<P<N$. Actually, ...


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This represents the probability over all $K$ that $A$ given an oracle access to $F_K(\cdot)$ outputs 1. You usually compare that to the probability of A ouptputting 1 while having oracle access to a random function and the difference tells you how well $A$ does at telling $F_K$ from random


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If you can read the intermediate states of the encryption algorithm you could recover, one by one all the round keys. Given a AES round, all the operation between the two AddRoundKey (at the beginning and the ond of the round) are invertible. Take for example round 1: you get the internal state before AddRoundKey (of round 2), you get back at the beginning ...


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The approach with which I solved the problem is indeed as @tylo suggested. Initially we know that the target plaintext $P$ is within the bounds $[0,N]$ where the lower bound $LB=0$ and the upper bound $UB=N$. Now we iterate the following algorithm $log_{2}N$ times to find P from the original intercepted ciphertext $C$ $C' = (2^{e}\mod N) * C$ if ...


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Prove? Why does the attacker need to "prove" it? For example, the attacker can check whether there is an oracle by looking at the code and seeing whether such an attack is possible. Or, the attacker can guess that such an attack might be possible and then try the attack. If the attack succeeds, the attacker knows the system is vulnerable. There might ...



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