Free online courseCryptography and Network Security

Course Description

Modern cybersecurity depends on one foundational skill: understanding how information is protected, transmitted, and attacked across networks. This free online course in Cryptography and Network Security is designed to help you build that foundation from the ground up, connecting core security principles with the mathematics and mechanisms that make secure communication possible.

You will start by clarifying what security actually means in practice through the CIA triad, common threat types, and the OSI security architecture. From there, you will develop a structured view of how security services and mechanisms fit into a network security model, so you can reason about confidentiality, integrity, authentication, and availability in real systems instead of treating them as abstract buzzwords.

A major strength of the course is how it bridges conceptual understanding and hands-on reasoning. You will explore cryptography essentials, key terms, and the mindset behind cryptanalysis, including brute-force approaches and traffic analysis. By working through classical techniques such as substitution, transposition, and polyalphabetic methods, you will see how encryption evolved, why early ciphers fail against modern analysis, and what design goals later algorithms needed to satisfy.

To move from intuition to competence, the course reinforces the math that underpins secure protocols. You will practice modular arithmetic, modular exponentiation, the Euclidean and extended Euclidean algorithms, multiplicative inverses, and important results such as Fermat’s little theorem and Euler’s theorem. Topics like primitive roots, the discrete logarithm problem, primality testing, and the Chinese remainder theorem help explain why certain cryptographic schemes are feasible while others are hard to break.

With these tools in place, you will understand how modern symmetric cryptography works through the structure and security properties of block ciphers and stream ciphers, including key design ideas such as the Feistel structure and the avalanche effect. You will also examine DES and AES at a practical level, learning how their rounds, transformations, and key expansion contribute to security. Finally, you will connect encryption to real deployments by studying modes of operation (ECB, CBC, CFB, OFB, CTR) and why choosing the right mode matters for both confidentiality and reliability.

By the end, you will be able to interpret how cryptographic components fit into broader network defense practices, evaluate common misconceptions, and make better security decisions in study projects, IT environments, and cybersecurity career pathways.