Textbook in PDF format

These are lecture notes for lecture notes for an introductory but fast-paced undergraduate/beginning graduate course on cryptography. I am using these notes for Harvard CS 127.
In this fast-paced course, I plan to start from the very basic notions of cryptography and by the end of the term reach some of the exciting advances that happened in the last few years such as the construction of fully homomorphic encryption, a notion that Brian Hayes called “one of the most amazing magic tricks in all of computer science”, and indistinguishability obfuscators which are even more amazing. To achieve this, our focus will be on ideas rather than implementations and so we will present cryptographic notions in their pedagogically simplest form – the one that best illustrates the underlying concepts – rather than the one that is most efficient, widely deployed, or conforms to Internet standards. We will discuss some examples of practical systems and attacks, but only when these serve to illustrate a conceptual point