Lecture 4: Symmetric Ciphers

This lecture introduces some of the basic principles of cryptography and explores symmetric ciphers, our primary tool for encrypting data. It considers the requirements we have for cipher keys and examines the feasibility of brute-force methods for finding keys. It also considers the importance of selecting an appropriate cipher mode when encrypting data.

A large part of the lecture is concerned with AES, the Advanced Encryption Standard. A broad overview of how AES is works is given, then the lecture concludes with an examination of how AES is integrated with message authentication in AEAD: Authenticated Encryption with Associated Data.