This paper presents Crypto-Tutor, a tool for learning modern cryptographic algorithms. Our tool offers an interactive way to learn about the uses and structure of several popular cryptographic algorithms, as well as the underlying mathematical concepts which guarantee the security of these algorithms. Crypto-Tutor also offers performance benchmarking of the algorithms for several datasets, as well as an interactive environment where the algorithms can be executed for custom input and configuration. This tool was used in the classroom, as part of two undergraduate courses in the Faculty of Technical Sciences, University of Novi Sad. Here we also present our experiences with using Crypto-Tutor in the classroom, and formally evaluate the usefulness of this tool.