Quoting Ken Raeburn <raeburn at MIT.EDU>: > On Oct 15, 2009, at 15:56, John Border wrote: > > I have what I thought was a simple question about the properties > > of AES. But, I have not been able to find an answer. Possibly that > > means the question itself is flawed (but I haven?t been able to > > figure that out either)? > > > > With AES, does the order of the functions matter, i.e. does > > EK(DK(P)) = DK(EK(P))? > As Ken responded, if the plaintext is a multiple of the block size, because EK and DK are inverses, the result is the identity function, so the answer to the above is that the order does not make a difference. BUT, I expect what you might have been trying to ask is whether EK1(DK2(P)) = DK2(EK1(P)), i.e. your question above, but using two different keys. In this case, the analyses is not as simple, and I would guess that the answer is that no they are not the same. But I could be wrong. You should be able to verify the "NO" answer with a simple experiment. Clifford Neuman
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