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I have made a python code for one DES rotation. Can I use the resulting cipher text as a plain text for the same rotation with the same key? I think the answer is no, I can't do so. But I need to be sure, an explanation will be very helpful.

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You could always do it, and if it fails, try to figure out why. –  rath Dec 18 '13 at 22:55
    
Hmmm..Then why do we use 16 permutations and not any other number? And Why does the Permutation tables have those values? Aren't they adjusted to fit just 16 permutations? –  Mohamed Ahmed Dec 18 '13 at 23:35
    
what do you mean by "rotation"? if you mean full block encryption with all rounds then yes there are methods –  Richie Frame Dec 19 '13 at 5:14
    
@Richie Frame, No I mean one "round" only of the 16 rounds, this picture illustrate what I mean. –  Mohamed Ahmed Dec 19 '13 at 6:58
    
You may want to rewrite the question, as I understand it the answer is "of course you can there is nothing to stop you". Also the permutation table has nothing to do with round count, is is designed to distribute bits across the s-boxes of the next round. –  Richie Frame Dec 19 '13 at 9:39

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Yes, you can, but it's insecure. DES has a different key schedule for each round to avoid linearity and meet-in-the-middle attacks. Also you reduce the strenght of your cipher since not all encryption round embed the whole key. Be aware that you need to swap left part and right part of your data material after each round otherwise it's going to be terribly insecure.

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