2.3, due on September 13

1. (Difficult) I was confused about the explanation about how to find the key length. I understand that the dot product when A_i is multiplied by A_i is the highest, but I am still confused about how that relates to the matching up of the letters when displacing the message. Also, finding the key using the second method was more confusing than the displacement and frequency analysis, and still is a little unclear.

2. (Reflective) I had never heard of the Vigenere Cipher, but I think it is a good idea. The fact that all you need for the key is one word is impressive. It doesn't surprise me that it was thought to be secure for that length of time. It would be a hard message to simply look at and break; thus, it is even more impressive that people have come up with methods to break the code. Even though the reasoning confuses me a little, I find it really cool that you can find the length of the key simply by the coincidences in matching letters when using displacement.