Lecture
This lecture covers the topics of cryptanalysis in public-key systems, focusing on ElGamal signatures and the security implications if certain checks are missed. It also delves into the power of interaction in interactive proofs, exploring concepts like CO-NP and NP classes, P vs. NP problems, Karp reduction, and NP-hardness. The instructor discusses the Goldwasser-Micali-Rackoff protocol, sequential composition in interactive proof systems, and tricky aspects of parallel composition. Through examples like the Coin Flipping Game and the DD Protocol, the lecture illustrates the practical applications and challenges of interactive systems and proofs.