Information security With resolved Exercises

This book presents a foundational exploration of information security through the lens of cryptography, moving from classical to modern systems. It begins by illustrating symmetric key encryption with the Hill cipher, which transforms data using linear algebra, and introduces the concept of perfect secrecy with the one-time pad, while noting its practical limitations in key management. The core of the text then delves into public-key cryptography, exemplified by RSA, which solves the key distribution problem through mathematically linked public and private keys. Throughout the examples, the book emphasizes critical practical lessons: the necessity of using sufficiently large keys, the importance of proper encoding and padding, and the fact that security relies not only on strong algorithms but also on robust implementation and key protection. Ultimately, it frames information security as a dynamic, layered discipline that requires constant adaptation to balance confidentiality, integrity, and availability against evolving threats.