3.2 Development of the Tools.............................. 5

In 1949, Shannon published the paper ”Communication theory of secrecy systems”. This constituted a foundational treatment and analysis of encryption systems. He transferred the methods of information theory, originally developed as a mathematical model for communication over ”noisy ” channels to the setting of cryptosystems. We give a brief introduction into his most outstanding ideas, such as the notions of perfect/provable security, and statistical/information-theoretic concepts like entropy, key equivocation, and unicity distance