Lecture
This lecture delves into the formalism of symmetric encryption systems, starting with block ciphers and their components such as key spaces and block spaces. It explains the correctness notion of block ciphers and introduces the concept of variable length symmetric encryption. The lecture also covers nonce-based encryption, deterministic algorithms, and the security definitions against key recovery and chosen plaintext attacks. Additionally, it explores the notion of security against distinguishers and the importance of commitment schemes in cryptographic protocols.