This companion book exercises and solutions for Classical Introduction to Cryptography: Applications for Communications Security contains a version with careful revision of teaching materials used by the author and given as examinations to advanced-level students Cryptography and Security Lecture at EPFL from 2000 to mid -2005. Exercise does not require extensive background in mathematics, because the ideas of the most important thing is to be introduced and discussed in a lot of practice. The author hopes the reader feel comfortable with the basic facts of discrete probability theory, discrete mathematics, calculus, algebra, and computer science.