# Due Friday September 4th

Due Friday:

• To know:  The libraries are scanning chapters of the textbook for me to upload to canvas.  But I can only have one or two on there at a time.  So if you’d like to read Chapter 2, please access it soon, as it will eventually get taken down.  The relevant parts of Chapter 2 for the course right now are: intro, 2.1, 2.2, 2.3, 2.4, 2.6, 2.7, 2.9, 2.12.  I’ve done some picking-and-choosing, so what I’ve covered in notes/class/videos/exercises is the official material, not the book.  But the book should provide a good backup resource and alternate explanation for lots of what I’ve done.
• To know:  The assessment for this module will open tomorrow and be due Thursday September 10th.  After that there’ll be a chance to correct your errors for some increase in credit.  The material covered is:
• Caesar cipher and cryptanalysis (frequency analysis)
• Vigenere cipher and cryptanalysis (including why it works)
• Affine cipher and cryptanalysis
• Hill cipher (how to encrypt/decrypt, cryptanalysis)
• AFDGVX cipher (how to encrypt/decrypt)
• enigma (generalities, history)
• terminology as covered in the slides of Wed Sept 2 (transposition cipher, block cipher, diffusion, etc. etc.)
• DES (generalities, history)
• modular arithmetic, to use in practice (addition, multiplication, powers, inverses using a multiplication table)
• modular arithmetic, the mathematical rigor to the definition (e.g. why the operations are well-defined), definitions of invertible, inverses, unit group.
• To know:  the next class will be an introduction to Sage.  I’ll have a worksheet ready to go; you’ll need a web browser to log in and participate.
• To know:  If you are interested in classical cryptography, a nice textbook with lots of history and details is “Secret History: The Story of Cryptology” by Craig P. Bauer.  Here’s a super-cool short Numberphile video about Enigma Machine.
• To do:  If you missed the last few minutes of class on Wednesday (I went overtime by 5 minutes), review those last minutes on the canvas video.
• To do:  Compare your answers to the Exercises from the last daily to these solutions.  If you still have any questions, contact me (or your peers) on discord (or email).
• To do:  Here are some exercises (tex) to hand in on the daily dropbox.  You may wish to use the Hill Cipher Tools part of the course webpage, to avoid by-hand matrix calculations.
• Purely, optionally, for fun:  PSNAABAEDLEDNIONPLESMELUIOEAEEMATCO (Key: one inch and a standard can of beans.)