1 Introduction 1 1.1 Alice, Bob, Eve, and the others . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 The Pre-history of Encryption . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Perfect Security and One-Time Pad . . . . . . . . . . . . . . . . . . . . . . 5 2 Notions of Security 7 2.1 Semantic Security . . . . . . . . . . .....