This textbook offers the knowledge and the mathematical background or techniques that are required to implement encryption/decryption algorithms or security techniques. It also provides the information on the cryptography and a cryptosystem used by organizations and applications to protect their data and users can explore classical and modern cryptography. The first two chapters are dedicated to the basics of cryptography and emphasize on modern cryptography concepts and algorithms. Cryptography terminologies such as encryption, decryption, cryptology, cryptanalysis and keys and key types...