Practical Cryptography

Practical Cryptography: From Classical Ciphers to Post-Quantum Standards is a hands-on introduction to modern cryptography designed for students, developers, and security practitioners who want to understand how cryptographic systems work in practice.

Rather than focusing solely on theory, this book emphasizes implementation and experimentation. Readers learn by writing and analyzing real programs in Python and Java, exploring both classical cryptographic ideas and the modern algorithms that protect today's digital systems.

The book begins with historical and classical ciphers that introduce the fundamental ideas behind encryption and code breaking. It then develops the mathematical foundations needed for modern cryptography, including modular arithmetic and number-theoretic algorithms. Building on this foundation, readers explore symmetric cryptography, hash functions, public-key systems such as RSA, and the practical use of digital signatures.

The final chapters introduce post-quantum cryptography, including lattice-based schemes such as ML-KEM (Kyber) and ML-DSA (Dilithium), which are part of the emerging standards designed to remain secure in the presence of quantum computers.

Throughout the book, numerous programming examples and exercises allow readers to experiment with cryptographic algorithms, measure their performance, and observe both their strengths and potential pitfalls.

Topics covered include:

• Classical ciphers and cryptanalysis

• Modular arithmetic and number theory for cryptography

• Symmetric encryption and modes of operation

• Hash functions and message authentication

• RSA encryption and digital signatures

• Implementation pitfalls and security considerations

• Post-quantum cryptography and modern standards

All source code used in the book is freely available in the accompanying GitHub repository, making it easy for readers to reproduce experiments and extend the examples.

This book is suitable for undergraduate and graduate courses in cryptography, as well as for programmers and security professionals who want a practical introduction to the algorithms that secure modern communication.