[17234] in cryptography@c2.net mail archive
New cipher used by iTunes
daemon@ATHENA.MIT.EDU (Charles M. Hannum)
Fri May 20 15:42:14 2005
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From: "Charles M. Hannum" <root@ihack.net>
To: cryptography@metzdowd.com
Date: Sun, 3 Apr 2005 09:43:27 +0000
I took a look at the new cipher used in iTunes 4.7, and spent some time
reducing it. The algorithm appears to have a similar structure to a 10-round
Twofish variant with fixed S-boxes, optimized via precomputed tables. I have
not fully analyzed what the permutation matrix and polynomial are, though.
There are a couple of strange changes. E.g., they had put the IV mixing
between the pre-whitening and post-whitening, but this turned out to
effectively cancel out and be equivalent to an altered version with a more
traditional CBC structure.
I'm including the current working implementation, along with some test
vectors, if anyone else wants to take a look at it.
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