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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]
In cryptography, confusion and diffusion are two properties of a secure cipher identified by Claude Shannon in his 1945 classified report A Mathematical Theory of Cryptography. [1] These properties, when present, work together to thwart the application of statistics , and other methods of cryptanalysis .
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]
Theory of cryptography refers to the study of cryptographic algorithms and protocols in a formal framework. The two main goals of the study are definitions and proofs of security. The two main goals of the study are definitions and proofs of security.
These ideas can be applied to a more realistic cryptography application. Peggy wants to prove to Victor that she knows the discrete logarithm of a given value in a given group. [11] For example, given a value y, a large prime p, and a generator , she wants to prove that she knows a value x such that g x ≡ y (mod p), without revealing x.
Kerckhoffs viewed cryptography as a rival to, and a better alternative than, steganographic encoding, which was common in the nineteenth century for hiding the meaning of military messages. One problem with encoding schemes is that they rely on humanly-held secrets such as "dictionaries" which disclose for example, the secret meaning of words.
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.
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 ...