Saturday, September 19, 2015

4.1, 4.2, and 4.4 Due Monday September 21

1)  The notation is pretty confusing to me.  I think that I am following the diagram, but I am wondering if the first half of the message, or in their example case, the first 6 bits are also dependent on the second half, or the the last 6 bits.  Because it looks like it is adding terms from both the L and the R (after it has been through the function) in order to get the next R bit.  I follow the diagram but I don't completely understand the notation.  I also don't completely understand the meaning of a permutation.

2) After looking at the DES algorithm and reading a little bit about it, I am impressed that people came up with such a secure and somewhat fast encryption method.  I also think it is pretty cool that although the DES algorithm is too long to discuss in the previous chapters, they could teach the same idea through a more simple example.  I am curious to learn more about differential analysis and how it works in order to break certain encryptions.

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