This is a companion exercise and solution book to A Classical Introduction to Cryptography: Applications for Communications Security (0-387-25464-1). Coverage includes symmetric or public-key cryptography cryptographic protocols design cryptanalysis and implementation of cryptosystems. Readers should be comfortable with basic facts of discrete probability theory discrete mathematics calculus algebra and computer science. However the exercises do not require an extensive background in mathematics since the most important notions are introduced and discussed in many of them. Exercises related to the more advanced parts of the textbook are marked with a star.