udfrg2
Reputation
Next privilege 50 Rep.
Comment everywhere
5
Impact
~349 people reached

• 0 posts edited

# 22 Actions

 May 30 accepted Is the following symmetric design secure? Nov 24 revised Is the following symmetric design secure? added 100 characters in body 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? spelling 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.