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May
30
accepted Is the following symmetric design secure?
Nov
24
revised Is the following symmetric design secure?
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Nov
24
awarded  Scholar
Nov
24
accepted What is the difference between a bijective random oracle and a random permutation?
Nov
23
comment Is the following symmetric design secure?
Thanks for this detailed answer. My aim really was to try to make the simplest scheme with perfect randomness. I do have ideas to make replay attacks infeasible, but I thought it would be too much for a single question since the real aim here was an attack to recover the input.
Nov
22
awarded  Supporter
Nov
22
revised What is the difference between a bijective random oracle and a random permutation?
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Nov
22
asked What is the difference between a bijective random oracle and a random permutation?
Nov
22
awarded  Informed
Nov
21
comment Is the following symmetric design secure?
@user8911 Well, according to my understanding, in a finite set, a random permutation is a random reversible oracle, so I'm fine with a random permutation. I also agree that with our modified Even-Mansour scheme, the same M leads to a different outputs each time. I was only speaking about the vanilla one. So this seems to basically boils down to decide whether $\oplus k1$ is equivalent to some randomness added to the input, isn't it?
Nov
21
comment Is the following symmetric design secure?
@user8911 Interesting link. In my case, isn't a reversible random oracle on a finite set equivalent to a random permutation? Also, the part I don't like about the Even-Mansour scheme is that if you encrypt twice the same message, the output will be the same (and if in some protocol, you have to often send a specific message, the attacker will know you are sending this specific message. He can then possibly get additional information from this...).
Nov
21
revised Is the following symmetric design secure?
typo
Nov
21
comment Is the following symmetric design secure?
@daniel I do agree that if the attacker makes you encrypt a single specific M||R, then he can get the key. However, R is not random any more if that case (that would mean the attacker is the random generator).
Nov
21
revised Is the following symmetric design secure?
deleted 6 characters in body
Nov
21
comment Is the following symmetric design secure?
@Ricky Demer Thanks for putting the right words. I've edited my question.
Nov
21
revised Is the following symmetric design secure?
added Ricky Demer improvements
Nov
20
awarded  Editor
Nov
20
awarded  Student
Nov
20
revised Is the following symmetric design secure?
added 16 characters in body
Nov
20
comment Is the following symmetric design secure?
Well, let's say the random oracle is a random bijection of a finite set. If you have as much time as you want, you can map the inverse of this oracle. Let us assume here that we know the inverse.