Chapters 3.8, 2.5-2.8 for lecture on 16 Sept

1. The difficult part of this passage was about how to crack the playfair and ADGFX ciphers from the plaintext only. It did not seem like there was a straightforward algorithm but took some educated guesses.

2. The block cipher was very interesting. I had seen it previously. It was fun to see that it could be very vulnerable under the attacks of known or chosen plaintext.