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Handbook of Applied Cryptography

The proliferation of computers and communications systems in the 1960s brought with it a demand from the private sector for means to protect information in digital form and to provide security services. Beginning with the work of Feistel at IBMin the early 1970s and culminating in 1977 with the adoption as a U.S. Federal Information Processing Standard for encrypting unclassified information, DES, the Data Encryption Standard, is the most well-known cryptographic mechanism in history. It remains the standard means for securing electronic commerce for many financial institutions around the world. | Chapter 1 Overview of Cryptography Contents in Brief 1.1 Introduction . 1 1.2 Information security and cryptography 2 1.3 Background on functions 6 1.4 Basic terminology and concepts . 11 1.5 Symmetric-key encryption . 15 1.6 Digital signatures 22 1.7 Authentication and identi®cation 24 1.8 Public-key cryptography 25 1.9 Hash functions . 33 1.10 Protocols and mechanisms . 33 1.11 Key establishment, management, and certi®cation . 35 1.12 Pseudorandom numbers and sequences 39 1.13 Classes of attacks and security models . 41 1.14 Notes and further references 45 1.1 Introduction Cryptography has a long and fascinating history. The most complete non-technical account of the subject is Kahn's The Codebreakers. This book traces cryptography from its initial and limited use by the Egyptians some 4000 years ago, to the twentieth century where it played a crucial role in the outcome of both world wars. Completed in 1963, Kahn's book covers those aspects of the history which were most signi®cant (up to that time) to the devel- opment of the subject. The predominant practitioners of the art were those associated with the military, the diplomatic service and government in general. Cryptography was used as a tool to protect national secrets and strategies. The proliferation of computers and communications systems in the 1960s brought with it a demand from the private sector for means to protect information in digital form and to provide security services. Beginning with the work of Feistel at IBM in the early 1970s and culminating in 1977 with the adoption as a U.S. Federal Information Processing Standard for encrypting unclassi®ed information, DES, the Data Encryption Standard, is the most well-known .