Thanks for catching the error in the first problem set. Here's the corrected version: Problem Set 1 (Word) and Problem Set 1 (PDF).

Also, here are copies of the two Excel files I used in class today: Modular Arithmetic and Decimation Cipher.

Finally, I meant to share during class something that I bookmarked this morning, a story on the hacking of Keurig's new scheme for preventing competitors from making coffee pods that work in Keurig coffee machines. I'll call this an example of cryptanalysis, since Keurig's scheme essentially involved encrypted messages between coffee pod and coffee maker. Keurig's competitors have now broken that encryption and are able to send messages of their own -- not unlike how Sir Francis Walsingham sent fake messages to Mary Queen of Scots and her conspirators.