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D'Agapeyeff Cipher
The D'Agapeyeff cipher is an as-yet unbroken cipher that appears in the first edition of ''Codes and Ciphers'', an elementary book on cryptography published by the Russian-born English cryptographer and cartographer Alexander D'Agapeyeff in 1939. Offered as a "challenge cipher" at the end of the book, the ciphertext is: It was not included in later editions, and D'Agapeyeff is said to have admitted later to having forgotten how he had encrypted it. Use of nulls in ciphertext It is possible that not all the ciphertext characters are used in decryption and that some characters are nulls. Evidence for this is given by the author on p. 111 of the text under the sub-section heading ''Military Codes and Ciphers'': "The cipher is of course easily made out, but if every third, fourth, or fifth letter, as may be previously arranged, is a dummy inserted after a message has been put into cipher, it is then extremely difficult to decipher unless you are in the secret." While t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cipher
In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is ''encipherment''. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography. Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. There are exceptions and some cipher systems may use slightly more, or fewer, characters when output versus the number that were input. Codes operated by substituting according to a large codebook which linked a random string of characters or numbers to a word or phrase. For example, "UQJHSE" could be the code for "Proceed to the following ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptographer
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adversarial behavior. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others. Core concepts related to information security ( data confidentiality, data integrity, authentication, and non-repudiation) are also central to cryptography. Practical applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications. Cryptography prior to the modern age was effectively synonymous with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartographer
Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an imagined reality) can be modeled in ways that communicate spatial information effectively. The fundamental objectives of traditional cartography are to: * Set the map's agenda and select traits of the object to be mapped. This is the concern of map editing. Traits may be physical, such as roads or land masses, or may be abstract, such as Toponomy, toponyms or political boundaries. * Represent the terrain of the mapped object on flat media. This is the concern of map projections. * Eliminate characteristics of the mapped object that are not relevant to the map's purpose. This is the concern of Cartographic generalization, generalization. * Reduce the complexity of the characteristics that will be mapped. This is also the concern of generaliza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Cipher
A null cipher, also known as concealment cipher, is an ancient form of encryption where the plaintext is mixed with a large amount of non-cipher material. Today it is regarded as a simple form of steganography, which can be used to hide ciphertext. This is one of 3 categories of cipher used in classical cryptography along with Substitution ciphers and Transposition ciphers. Classical cryptography In classical cryptography, a ''null'' is intended to confuse the cryptanalyst. In the most common form of a null cipher, the plaintext is included within the ciphertext and one needs to discard certain characters in order to decrypt the message (such as first letter, last letter, third letter of every second word, etc.) Most characters in such a cryptogram are nulls, only some are significant, and some others can be used as pointers to the significant ones. Here is an example null cipher message, sent by a German during World War I: Taking the first letter of every word reveals the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Index Of Coincidence
In cryptography, coincidence counting is the technique (invented by William F. Friedman) of putting two texts side-by-side and counting the number of times that identical letters appear in the same position in both texts. This count, either as a ratio of the total or normalized by dividing by the expected count for a random source model, is known as the index of coincidence, or IC for short. Because letters in a natural language are not distributed evenly, the IC is higher for such texts than it would be for uniformly random text strings. What makes the IC especially useful is the fact that its value does not change if both texts are scrambled by the same single-alphabet substitution cipher, allowing a cryptanalyst to quickly detect that form of encryption. Calculation The index of coincidence provides a measure of how likely it is to draw two matching letters by randomly selecting two letters from a given text. The chance of drawing a given letter in the text is (number of time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Letter Frequency
Letter frequency is the number of times letters of the alphabet appear on average in written language. Letter frequency analysis dates back to the Arab mathematician Al-Kindi (c. 801–873 AD), who formally developed the method to break ciphers. Letter frequency analysis gained importance in Europe with the development of movable type in 1450 AD, where one must estimate the amount of type required for each letterform. Linguists use letter frequency analysis as a rudimentary technique for language identification, where it is particularly effective as an indication of whether an unknown writing system is alphabetic, syllabic, or ideographic. The use of letter frequencies and frequency analysis plays a fundamental role in cryptograms and several word puzzle games, including Hangman, ''Scrabble'', ''Wordle'' and the television game show ''Wheel of Fortune''. One of the earliest descriptions in classical literature of applying the knowledge of English letter frequency to sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polybius Square
The Polybius square, also known as the Polybius checkerboard, is a device invented by the ancient Greeks Cleoxenus and Democleitus, and made famous by the historian and scholar Polybius. The device is used for fractionating plaintext characters so that they can be represented by a smaller set of symbols, which is useful for telegraphy, steganography, and cryptography. The device was originally used for fire signalling, allowing for the coded transmission of any message, not just a finite amount of predetermined options as was the convention before. Basic form According to Polybius' ''Histories,'' the device was invented by Cleoxenus and Democleitus, and further developed by Polybius himself. The device partitioned the alphabet into five tablets with five letters each (except for the last one with only four). There are no surviving tablets from antiquity. Letters are represented by two numbers from one to five, allowing the representation of 25 characters using only 5 numeric sym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elonka Dunin
Elonka Dunin (; born December 29, 1958) is an American video game developer and cryptologist. Dunin worked at Simutronics Corp. in St. Louis, Missouri from 1990–2014, and in 2015 was Senior Producer at Black Gate Games in Nashville, Tennessee. She is Chairperson Emerita and one of the founders of the International Game Developers Association's Online Games group, has contributed or been editor in chief on multiple IGDA State of the Industry white papers, and was one of the Directors of the Global Game Jam from 2011–2014. As of 2020 she works as a management consultant at Accenture. Dunin has published a book of exercises on classical cryptography, and maintains cryptography-related websites about topics such as ''Kryptos'', a sculpture at the Central Intelligence Agency containing an encrypted message, [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nick Pelling
Nick Pelling is a British-born computer programmer and investigative writer best known as the creator of the 1984 game '' Frak!''."Desert Island Disks: Nick Pelling". ''Retro Gamer'' 26, pp. 82-85. Games Developed As Aardvark Software * ''Arcadians'' (1982) * ''Zalaga'' (1983) (port of Galaga) * '' Frak!'' (1984) * '' Firetrack'' (1987) * '' Sharkey's 3D Pool'' (1989) * ''3D Pocket Pool'' (2001) Independently * '' Bangkok Knights'' (1987) * ''Shinobi'' (1989) * '' Loopz'' (1990) * '' Terminator 2: Judgment Day'' (1993) * '' The Simpsons: Bartman Meets Radioactive Man'' (1993) * ''The Pagemaster'' (1994) * ''Mortal Kombat II'' (1994) * '' Wolverine: Adamantium Rage'' (1994) * ''Primal Rage'' (1995) * ''Batman Forever'' (1995) * ''The X-Files Game'' (1999) * '' In Cold Blood'' (2000) * ''Street Fighter Alpha 3'' (2002) * '' Kelly Slater's Pro Surfer'' (2002) * ''Championship Manager 5'' (2005) * '' Buzz!: The Music Quiz'' (2005) * '' Buzz!: The BIG Quiz'' (2006) * '' B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Cryptogram Association
The American Cryptogram Association (ACA) is an American non-profit organization devoted to the hobby of cryptography, with an emphasis on types of codes, ciphers, and cryptograms that can be solved either with pencil and paper, or with computers, but not computer-only systems. History The ACA was formed on September 1, 1930. Initially the primary interest was in monoalphabetic substitution ciphers (also known as "single alphabet" or "Aristocrat" puzzles), but this has since extended to dozens of different systems, such as Playfair, autokey, transposition, and Vigenère ciphers. Since some of its members had belonged to the “National Puzzlers' League”, some of the NPL terminology ("nom," "Krewe," etc.) is also used in the ACA. Publications and activities The association has a collection of books and articles o ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
