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Definition: Cryptography from Dictionary of Information Science and Technology

a study of making a message secure through encryption; secret key and public key are the two major camps of cryptographic algorithms. In secret key cryptography, one key is used for both encryption and decryption, while in public key cryptography, two keys (public and private) are used. (Chen, 2009e)

Summary Article: cryptography
From The Columbia Encyclopedia

(krĭptŏg'rӘfē) [Gr.,=hidden writing], science of secret writing. There are many devices by which a message can be concealed from the casual reader, e.g., invisible writing, but the term cryptography strictly applies to translating messages into cipher or code. The science of breaking codes and ciphers without a key is called cryptanalysis. Cryptology is the science that embraces both cryptography and cryptanalysis. In enciphering, each letter of the message is replaced by another letter or figure; in encoding, syllables, words, or whole sentences are treated. The code is the agreed upon set of rules whereby messages are converted from one form to another. The beginnings of cryptography can be traced to the hieroglyphs of early Egyptian civilization (c.1900 B.C.). Ciphering has always been considered vital for diplomatic and military secrecy; the Bible is replete with examples of ciphering, and many figures throughout history have written in ciphers, including Julius Caesar, Charlemagne, Alfred the Great, Mary Queen of Scots, and Louis XIV. Francis Bacon's celebrated biliteral cipher (1605) was an arrangement of the letters a and b in five-letter combinations, each representing a letter of the alphabet. This code illustrates the important principle that a code employing only two different signs can be used to transmit information. In the 20th cent. mathematical theory and computer science have both been applied to cryptanalysis. As the science of cryptology becomes increasingly sophisticated, most nations have found it necessary to develop special governmental bureaus to handle diplomatic and military security, e.g., the National Security Agency in the United States. The widespread use of computers and data transmission in commerce and finance is making cryptography very important in these fields as well. Recent successes in applying certain aspects of computer science to cryptography seem to be leading to more versatile and more secure systems in which encryption is implemented with sophisticated digital electronics. Industry and the U.S. government, however, have argued over who will have ultimate control over data encryption and, as a result, over government access to encrypted private transmissions.

• See , Cryptanalysis (1956);.
• , Secret Writing (1970);.
• , Cryptography and Data Security (1982);.
• ; , Machine Cryptography and Modern Cryptoanalysis (1985);.
• , The Codebreakers (rev. ed. 1996);.
• , The Code Book (1999).
The Columbia Encyclopedia, © Columbia University Press 2018

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