2.3, due on September 13

1. (Difficult) I thought the frequency analysis by multiplying vectors was a little challenging.  I think that if I end up needing to do math like that, I should be able to, but I don't think that my mind is wrapped around why it works, yet.  The first key finding approach, where you start with "e" made a little more sense than the second approach and why finding the key length works.  Probably if I thought more about the first approach, and then tried the others, it could make sense.
2. (Reflective) It is interesting that this cipher was thought secure for a long time.  It is basically what my group, and probably many others did for their projects.  I couldn't initially think of a good way to break our cipher, with only the ciphertext, but now I see how it could be done.
   It is also interesting that a similar idea seems to be used with more modern ciphers where key material is combined with each byte.  I think this is true of stream ciphers and the theoretical one-time pads, at least?  I wonder if modern approaches considered the Vigenère cipher when they were being developed.