Andrew McCartney

Originally written for Algebra 2 students as a fun end-of-year after-testing activity. It's a lighthearted take on the subject but includes some more serious math. This is a 58-page mini-textbook that covers some basic elements of classical cryptography, including Caesar, vigenere, affine, and keyword ciphers, among others. It discusses modular arithmetic, solving algebraic equations with modular arithmetic, and some basic work with prime numbers (coprimes, Ulam's spiral, Mersenne Primes). The