Cryptography is often perceived as a highly mathematical subject, making it challenging for many learners to grasp. Recognizing this, the book has been written with a focus on accessibility, requiring minimal prerequisites in number theory or algebra. The book, aims to explain cryptographic principles and how to apply and develop cryptographic algorithms and systems. The book comprehensively covers symmetric and asymmetric ciphers, hashes, digital signatures, random number generators, authentication schemes, secret sharing schemes, key distribution, elliptic curves, and their practical applications. To simplify the subject, the book begins with an introduction to the essential concepts of number theory, tailored for students with little to no prior exposure. The content is presented with an algorithmic approach and includes numerous illustrative examples, making it ideal for beginners as well as those seeking a refresher. Overall, the book serves as a practical and approachable guide to mastering the subject.