A comprehensive introduction to the fundamentals of provable security for advanced undergraduates. This accessible textbook provides a comprehensive introduction to the algorithms that keep our digital lives safe--how they work, what makes them different, and why they are secure. Mike Rosulek focuses on provable security--the process of defining what it means to be secure and mathematically proving security properties--to demystify the study of cryptography. Writing with clarity and humor, Rosulek covers basic building blocks before moving to symmetric-key encryption and authentication, public-key cryptography, and advanced topics. Employing a novel pseudocode-based approach to learning provable security and security proofs, The Joy of Cryptography empowers anyone with a small amount of programming experience to reason formally about security properties. Uses pseudocode-based reasoning to make provable security accessible to undergraduates Focuses on proven methods used in practice today Offers rigorous treatment of symmetric-key and public-key encryption and authentication Includes advanced material on encrypted messaging, post-quantum cryptography, and zero-knowledge proofs Features extensive ancillary resources.