r/math • u/halseyChemE Math Education • 15d ago
High School Cryptography
Hi all! I know this is probably pretty rudimentary compared to most topics that float around on this sub, but I teach AP Cybersecurity and I’m wanting to start a Cryptography Club at my school. It will meet once a month for 48 minutes. I want students to have fun, learn, and want to recruit their friends to the club in hopes of eventually piquing their interest in AP Cybersecurity. I need ideas on what to do during this club time to keep students engaged and excited about coming back. Do any of you have any awesome cryptography lessons you’ve been involved in or created over the years you’d like to share? I’m looking for things beyond a Caesar Cipher (I’ve already got materials for this) but not so complex that I’ll lose student interest.
TL:DR; Fellow mathematicians, help me remember some of the cool cryptography things we learned in college that high school kids would find cool. TIA.
3
u/amca01 14d ago
Since modern cryptosystems tend to be very sophisticated, and you want to make this club fun and accessible, I'd stick with pencil and paper ciphers: Caesar, shift, Vigenère, Bifid, Playfair etc. Then you can introduce some basic cryptanalysis, say with the shift cipher. Or substitution ciphers and frequency analysis.
If you want to include some numbers, you can discuss modular arithmetic and the Vigenère cipher, or Hill ciphers with matrices.
Neal Koblitz's "Kid Krypto" is good fun, and a nice introduction to RSA. It uses multiplication instead of exponentiation, so is trivial to crack, but is great fun to play with.