Re: DES: left "circular shift" of key bits

On Sat, 25 Nov 2006 00:29:28 -0500 (EST), "Arthur J. O'Dwyer"
<ajonospam@xxxxxxxxxxxxxx> wrote:

On Fri, 24 Nov 2006, Mike McNally wrote:

In conjunction to reading Applied Cryptography 2nd Ed., I'm also using
Cryptool as a learning aid. In learning modern encryption algorithms I
figured I'd start with the DES, my logic being that it will give me a
good foundation for learning the rest of the algorithms.

However, I do have a question about the "circular shift" ...

(I have aligned the shift for simplicity)

For the 'R' half:

1 0 1 1 1 1 1
1 0 0 1 1 0 0
0 1 1 1 1 0 0
1 1 1 1 0 0 0

(The above four 8-bit numbers are apparently supposed to represent
one 32-bit number; dunno why you wrote it on four lines.)

Yes Arthur, you are correct. Cryptool, in the demonstration, represented the number
on 4 seperate lines for whatever reason. The obvious was right in my face and I
didn't even recongnize it. I think I have been looking at little diagrams, S boxes P
boxes and feistel-Chiffre process enough for today... time to take a break.
.

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