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The following outline is provided as an overview of and topical guide to cryptography: Cryptography (or cryptology) – practice and study of hiding information. Modern cryptography intersects the disciplines of mathematics, computer science, and engineering. Applications of cryptography include ATM cards, computer passwords, and electronic ...
David Kahn notes in The Codebreakers that modern cryptology originated among the Arabs, the first people to systematically document cryptanalytic methods. [15] Al-Khalil (717–786) wrote the Book of Cryptographic Messages, which contains the first use of permutations and combinations to list all possible Arabic words with and without vowels.
Cryptography, or cryptology (from Ancient Greek: κρυπτός, romanized: kryptós "hidden, secret"; and γράφειν graphein, "to write", or -λογία-logia, "study", respectively [1]), is the practice and study of techniques for secure communication in the presence of adversarial behavior. [2]
Historically, various forms of encryption have been used to aid in cryptography. Early encryption techniques were often used in military messaging. Since then, new techniques have emerged and become commonplace in all areas of modern computing. [1] Modern encryption schemes use the concepts of public-key and symmetric-key. [1]
This concept is widely embraced by cryptographers, in contrast to security through obscurity, which is not. Kerckhoffs's principle was phrased by American mathematician Claude Shannon as "the enemy knows the system", [1] i.e., "one ought to design systems under the assumption that the enemy will immediately gain full familiarity with them".
It is one of the foundational treatments (arguably the foundational treatment) of modern cryptography. [2] His work has been described as a "turning point, and marked the closure of classical cryptography and the beginning of modern cryptography." [3] It has also been described as turning cryptography from an "art to a science". [4]
Symmetric key cryptography—compute a ciphertext decodable with the same key used to encode (e.g., AES) Public-key cryptography—compute a ciphertext decodable with a different key used to encode (e.g., RSA) Digital signatures—confirm the author of a message; Mix network—pool communications from many users to anonymize what came from whom
Cryptanalysis has coevolved together with cryptography, and the contest can be traced through the history of cryptography—new ciphers being designed to replace old broken designs, and new cryptanalytic techniques invented to crack the improved schemes. In practice, they are viewed as two sides of the same coin: secure cryptography requires ...