Lecture
This lecture covers the development of a theory of secrecy systems by C. E. Shannon in 1948. It discusses the mathematical structure and properties of concealment, privacy, and true secrecy systems. Various examples of ciphers such as simple substitution, transposition, Vigenère, and digram substitution are presented. The lecture also explores the concept of perfect secrecy in secret communication systems with shared secret keys, emphasizing the importance of entropy and independence in achieving perfect secrecy.