Due Wednesday:
 To Know: I’ll be posting the first module (classical cryptography) assessment this weekend and have it open for a week (I’ll make it due Monday, September 14). The info about it (topics covered; edited slightly) is in the previous daily post.
 To Know: If you had trouble with sage.colorado.edu (some people had the server kind of hang on them, or had trouble with tab complete or the ? command; for most it was fine), there’s an alternative called CoCalc (cocalc.com) where you can use Sage Mathematics Software for free. Unfortunately, sage.colorado.edu runs Python 2, Sage 8.4, whereas CoCalc is on Python 3, Sage 9.1. This means it can be a bit of work to transport a notebook from one spot to another. If you are computer savvy, it’s not hard to google, but I’m not going to post full instructions here. Likely, you’ll be fine if you just avoid the tab complete or ? command.
 To Know: What’s coming next is more modular arithmetic, and this will involve some more proofs. I will also begin to assign exercises that may really need the aid of basic computer algorithms to avoid impossibly long work by hand. I expect that most students have a solid grounding in _either_ proofs or coding, and some of you have both. If both, great! But the course expectation is that you’ll devote some time to strengthening your weak side. So please do expect that; I’ll just try to stream that work a little: keep reading.
 To Know: Here’s some description of what to cover to brush up:

 PROOFS: Chapters 47, 910 of Hammack’s Book of Proof provide a comprehensive overview of the proof methods studied in MATH 2001, and should be the main background needed for the course. If you need a refresher, you could do this concurrently through the next few weeks. I will set up “proofs club” where we meet as a group to do examples and talk about proofs.
 PROGRAMMING: If you’re new to programming, then you’ll want to make sure to set aside some time to work carefully through the rest of the Sage worksheet we started on Friday. It’s designed to cover basically everything you should need to do exercises in the class. But you’ll want to get more practice in the form of doing the Challenge problems in Section X. I will set up “programming club” where we can continue to work through this at a time that works for students.

 To do: Having read the above, drop me an email if you want to be part of “Proof Club” or “Programming Club”. We’ll set up zoom meetings to do some extra work making sure background in these areas is solid. All optional, but you do need these skills for the course. So if you want to be in on coordination for this, then opt in.
 To do: Compare your answers to the Hill Cipher exercises to my solutions.
 To do: Fill out my early feedback survey for the course.
 To do: Decrypt the following ADFGVX cipher by hand using the key shown in my slides, for practice. VXDGDGDGVGGADAFXXDXDXDAAAGAG. (BTW, Do you notice how the different columns prefer different letters? With reference to the video from class, remind yourself how this type of pattern can be used for cryptanalysis.)
 To do: Watch my YouTube video Modular Arithmetic: In Motion (18:47) and do the accompanying worksheet.
 For the canvas dropbox: upload the worksheet.