This article describes the author's experience designing and implementing an inquiry-based learning (IBL) pedagogical approach to an upper-division undergraduate cryptology course. The author shares the course goals and how the IBL style supports their achievement. The article concludes with sample activities -- in-class exercises that touch on one-time pad, the Birthday Problem, the Meet-in-the-Middle attack, and Diffie-Hellman key exchange protocol, and a programing assignment on the Vigenère cipher.