# Due Friday August 28th

For Friday, August 28th:

• Be aware that there’s a Cryptography Tools sheet available under Resources above.  It has a Vigenere square, among other things, to make adding mod 26 easy.
• Come up with a short (a few words) answer to the question “What’s the coolest math?”  This is your plaintext.
• Choose a 4-7 character word to use as a key.  Make it less than half the length of your plaintext.
• Encrypt the plaintext with Vigenere cipher (by hand, using the cryptography tools sheet if you like).
• Post your answer on the discord channel #ciphertexts in category STUDY GROUPS, along with the key.
• Choose another user’s post from #ciphertexts, and decrypt it (by hand).  Post the answer in the form “So-and-so thinks the coolest math is….”
• If by some chance you missed the daily post from yesterday, please catch up on it now.  Modular arithmetic is a bedrock concept for the rest of the course – absolutely crucial.
• I really do strongly encourage you to find partners to work with on discord.  You can watch the video below with someone so you can bounce ideas around.  Hop onto the text channel #study-room and just say “Hey all, I’m doing my daily post now.”  Chances are someone else might be around. Or just ask on there or on the #ask-the-hive channel when you have questions. 🙂
• Also, just be aware we are currently covering material that is in Chapter 2 of the text; you can use this as an added resource.  Chapter 3 contains some brief explanation of modular arithmetic.
• Watch my video Modular Arithmetic:  Under the Hood (17:26).  This gives an explanation for why everything works as described in the first video, so it should help demystify it a little.  And, it offers a glimpse of what type of mathematical proof I hope you can write, coming into the course.
• Therefore, your task is this:  study the proofs from the video to understand them, then turn off the screen and attempt to write the theorem statement and proof yourself, in your own words.  Turn on and compare, repeat, adjust, repeat.  This is not to hand in, but it’s an opportunity to get more comfortable with something we will rely on during the class.  Make sure none of the logical steps are mysterious — every one has a justification and a usefulness. Note: I could ask you to write these or similar proofs in an assessment.
• Your final task is to write me a brief note in today’s canvas dropbox about your comfort level with the proofs from the video.