CRYPTOGRAPHY INTRODUCTION.docx - 1 Introduction Cryptography is a subject that has been studied and applied since ancient Roman times and research into

CRYPTOGRAPHY INTRODUCTION.docx - 1 Introduction...

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1. Introduction Cryptography is a subject that has been studied and applied since ancient Roman times, and research into better encryption methods continues to this day. Cryptography is the art of encoding and decoding messages so that messages can be securely transmitted from a sender to a receiver without fear of an outside party intercepting and reading or altering the message's contents. The purpose of this paper is to describe the history and evolution of cryptography starting from the beginning of the 20th century and continuing into the present day. Specifically, the following five topics will be addressed: the cryptography used from 1900 until the end of World War II, the history of the politics involved with government control over cryptography, the history and current status of asymmetric cryptography, the history and current status of symmetric cryptography, and the future of the field of cryptography using quantum physics. 2. A Brief History of Cryptography The history of cryptography goes back thousands of years. Until recently, this history has consisted of the classical components of cryptography – ciphers written with pen on paper or other simple mechanical services. The turn of the 20th century however, brought about several advances in this subject. The invention of electromagnetic machines such as the German Enigma provided a much more efficient method of encrypting messages, and subsequently led to the introduction of cryptography into the emerging field of computing. “The fundamental objective of cryptography is to enable two people, usually referred to as Alice and Bob, to communicate over an insecure channel in such a way that an opponent, Oscar, cannot understand what is being said” (Zotos). A cipher is an algorithm for performing encryption (and in the reverse, decryption); it is in effect a series of well-defined steps that can be followed as a procedure. The original information is usually known as plaintext and the encrypted messages are known as cipher text. 2.1 Early Cryptography One of the oldest cipher styles is the substitution cipher, whose first examples are dated back thousands of years. Substitution is a method of encrypting by which units of plaintext are substituted with cipher text according to a regular system. An example of this is the Atbash cipher, which dates from 500 BC (Kartalopoulos). This cipher is based on the Hebrew alphabet, and is regulated where the first letter is substituted by the last letter, the second letter by the second to last letter and so on. Because it is a monoalphabetic cipher and can have only one possible key, this cipher is relatively weak; however this was not a viable concern during its time as literacy was not common. These types of ciphers were used frequently in religious texts and writings, and it was probably this use that developed the method of frequency analysis to analyze the messages (Kartalopoulos). Frequency analysis is where one examines the frequency of substituted letters, from which they can estimate certain letters which appear repeatedly in the plaintext language.
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