Saturday, September 21, 2013

Assignment 9

Perhaps the most difficult part of this reading assignment was the proof at the end, where we proved that DES is not a group.  I didn't quite understand that proof, but I assume that is mostly because I have not taken abstract algebra yet.  In general, I understood the section, but barely.  I feel like I have a tenuous hold on what the text was trying to say.

What was quite interesting to me was actually the proof I didn't understand.  The last part of the proof, where they show that m has to be greater than 10^(277), thus making DES not closed under composition was very interesting to me.  The proof used mainly a numerical method to show a theoretical result, or at least that's how it seemed to me.  Perhaps I misunderstood the proof, which is entirely possible, but either way, the method for doing this proof was quite interesting to me.  There are definitely more ways to prove things than I had before imagined.

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