Welcome to the CYP302 course!

This book offers a deep-dive introduction to the science and practice of cryptography. Where possible it focuses on conceptual, rather than formal exposition of the material.

This educational content is adapted from the book and repo JWBurgers. While the author has graciously permitted its educational use, all intellectual property rights remain with the original creator.

It is difficult to find many materials that offer a good middle ground in cryptography education.

On the one hand, there are lengthy, formal treatises, really only accessible to those with a strong background in mathematics, logic, or some other formal discipline. On the other hand, there are very high-level introductions that really hide too many of the details for anyone that is at least a bit curious.

This introduction to cryptography seeks to capture the middle ground. While it should be relatively challenging and detailed for anyone new to cryptography, it is not the rabbit hole of a typical foundational treatise.

From developers to the intellectually curious, this book is useful for anyone that wants more than a superficial understanding of cryptography. If your aim is to master the field of cryptography, then this book is also a good starting point.

The book currently contains seven chapters: "What is Cryptography?" (Chapter 1), "Mathematical Foundations of Cryptography I" (Chapter 2), "Mathematical Foundations of Cryptography II" (Chapter 3), "Symmetric Cryptography" (Chapter 4), "RC4 and AES" (Chapter 5), "Asymmetric Cryptography" (Chapter 6), and "The RSA cryptosystem" (Chapter 7). A final chapter, "Cryptography in Practice," will still be added. It focuses on various cryptographic applications, including transport layer security, onion routing, and Bitcoin's value exchange system.

Unless you have a strong background in mathematics, number theory is probably the most difficult topic in this book. I offer an overview of it in Chapter 3, and it also appears in the exposition of AES in Chapter 5 and the RSA cryptosystem in Chapter 7.

If you are really struggling with the formal details in these parts of the book, I recommend you settle for a high-level reading of them the first time around.

The most influential book in shaping this one has been Jonathan Katz and Yehuda Lindell’s Introduction to Modern Cryptography, CRC Press (Boca Raton, FL), 2015. An accompanying course is available on Coursera called "Cryptography."

The main additional sources that have been helpful in creating the overview in this book are Simon Singh, The Code Book, Fourth Estate (London, 1999); Christof Paar and Jan Pelzl, Understanding Cryptography, Springer (Heidelberg, 2010) and a course based on the book by Paar called “Introduction to Cryptography”; and Bruce Schneier, Applied Cryptography, 2nd edn, 2015 (Indianapolis, IN: John Wiley & Sons).

I will only cite very specific information and results I take from these sources, but want to acknowledge my general indebtedness to them here.

For those readers who wish to seek out more advanced knowledge on cryptography after this introduction, I highly recommend Katz and Lindell’s book. Katz's course on Coursera is somewhat more accessible than the book.

Please have a look at the contributions file in the repository for some guidelines on how to support the project.

Key terms in the primers are introduced by making them bold. For instance, the introduction of the Rijndael cipher as a key term would look as follows: Rijndael cipher.

Key terms are explicitly defined, unless they are proper names or their meaning is obvious from the discussion.

Any definition is usually given upon introduction of a key term, though sometimes it is more convenient to leave the definition until a later point.

Words and phrases are emphasized via italics. For instance, the phrase "Remember your password" would look as follows: Remember your password.

The formal notation mainly concerns variables, random variables, and sets.

Ready to explore the fascinating world of cryptography? Let's go!