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Trifid Cipher
The trifid cipher is a classical cipher invented by Félix Delastelle and described in 1902. Extending the principles of Delastelle's earlier bifid cipher, it combines the techniques of fractionation and transposition to achieve a certain amount of confusion and diffusion: each letter of the ciphertext depends on three letters of the plaintext and up to three letters of the key. The trifid cipher uses a table to ''fractionate'' each plaintext letter into a trigram, mixes the constituents of the trigrams, and then applies the table in reverse to turn these mixed trigrams into ciphertext letters. Delastelle notes that the most practical system uses three symbols for the trigrams:In order to split letters into three parts, it is necessary to represent them by a group of three signs or numbers. Knowing that ''n'' objects, combined in trigrams in all possible ways, give ''n'' × ''n'' × ''n'' = ''n''3, we recognize that three is the only value for ''n''; two would only give 23 = ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classical Cipher
In cryptography, a classical cipher is a type of cipher that was used historically but for the most part, has fallen into disuse. In contrast to modern cryptographic algorithms, most classical ciphers can be practically computed and solved by hand. However, they are also usually very simple to break with modern technology. The term includes the simple systems used since Greek and Roman times, the elaborate Renaissance ciphers, World War II cryptography such as the Enigma machine and beyond. In contrast, modern strong cryptography relies on new algorithms and computers developed since the 1970s. Types of classical ciphers Classical ciphers are often divided into ''transposition ciphers'' and ''substitution ciphers''. Substitution ciphers In a substitution cipher, letters (or groups of letters) are systematically replaced throughout the message for other letters (or groups of letters). A well-known example of a substitution cipher is the Caesar cipher. To encrypt a message with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Félix Delastelle
Félix-Marie Delastelle (2 January 1840 – 2 April 1902) was a French cryptographer, best known for inventing the bifid cipher, first presented in the ''Revue du Génie civil'' in 1895 under the name of "cryptographie nouvelle". This cipher combines fractionation with transposition, and was an early cipher to implement the principles of confusion and diffusion. David Kahn described it as a "system of considerable importance in cryptology." Delastelle's other polygraphic substitution ciphers included the trifid and four-square ciphers.Delastelle, p. 77. The last of these is a variant on the earlier Playfair cipher: Delastelle may have been unaware of Playfair, but he had certainly read of the fractionating cipher described by Pliny Chase Pliny Earle Chase (18 August 1820 in Worcester, Massachusetts – 17 December 1886 in Haverford, Pennsylvania) was an American scientist, mathematician, and educator who contributed to the fields of astronomy, electromagnetism, and cryptogr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bifid Cipher
In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion. It was invented around 1901 by Felix Delastelle. Operation First, a mixed alphabet Polybius square is drawn up, where the I and the J share their position: 1 2 3 4 5 1 B G W K Z 2 Q P N D S 3 I O A X E 4 F C L U M 5 T H Y V R The message is converted to its coordinates in the usual manner, but they are written vertically beneath: F L E E A T O N C E 4 4 3 3 3 5 3 2 4 3 1 3 5 5 3 1 2 3 2 5 They are then read out in rows: 4 4 3 3 3 5 3 2 4 3 1 3 5 5 3 1 2 3 2 5 Then divided up into pairs again, and the pairs turned back into letters using the square: 44 33 35 32 43 13 55 31 23 25 U A E O L W R I N S In this way, each ciphertext character depends on two plaintext characters, so the bifid is a digraphic cipher, like the Playfair cipher. To decrypt, the procedure is simply reversed. Longer messages are fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transposition Cipher
In cryptography, a transposition cipher is a method of encryption which scrambles the positions of characters (''transposition'') without changing the characters themselves. Transposition ciphers reorder units of plaintext (typically characters or groups of characters) according to a regular system to produce a ciphertext which is a permutation of the plaintext. They differ from substitution ciphers, which do not change the position of units of plaintext but instead change the units themselves. Despite the difference between transposition and substitution operations, they are often combined, as in historical ciphers like the ADFGVX cipher or complex high-quality encryption methods like the modern Advanced Encryption Standard (AES). General principle Plaintexts can be rearranged into a ciphertext using a key, scrambling the order of characters like the shuffled pieces of a jigsaw puzzle. The resulting message is hard to decipher without the key because there are many ways the char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Confusion And Diffusion
In cryptography, confusion and diffusion are two properties of the operation of a secure cipher identified by Claude Shannon in his 1945 classified report ''A Mathematical Theory of Cryptography'.'' These properties, when present, work to thwart the application of statistics and other methods of cryptanalysis. These concepts are also important in the design of secure hash functions and pseudorandom number generators where decorrelation of the generated values is the main feature. Definition Confusion Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two. The property of confusion hides the relationship between the ciphertext and the key. This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of most or all of the bits in the ciphertext will be affected. Confusion increases the ambiguity of ciphertext and it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigram
Trigrams are a special case of the ''n''-gram, where ''n'' is 3. They are often used in natural language processing for performing statistical analysis of texts and in cryptography for control and use of ciphers and codes. Frequency Context is very important, varying analysis rankings and percentages are easily derived by drawing from different sample sizes, different authors; or different document types: poetry, science-fiction, technology documentation; and writing levels: stories for children versus adults, military orders, and recipes. Typical cryptanalytic frequency analysis finds that the 16 most common character-level trigrams in English are: Because encrypted messages sent by telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ... often omit punctuation and spaces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substitution Cipher
In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution process to extract the original message. Substitution ciphers can be compared with transposition ciphers. In a transposition cipher, the units of the plaintext are rearranged in a different and usually quite complex order, but the units themselves are left unchanged. By contrast, in a substitution cipher, the units of the plaintext are retained in the same sequence in the ciphertext, but the units themselves are altered. There are a number of different types of substitution cipher. If the cipher operates on single letters, it is termed a simple substitution cipher; a cipher that operates on larger groups of letters ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartesian Coordinates
A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured in the same unit of length. Each reference coordinate line is called a ''coordinate axis'' or just ''axis'' (plural ''axes'') of the system, and the point where they meet is its ''origin'', at ordered pair . The coordinates can also be defined as the positions of the perpendicular projections of the point onto the two axes, expressed as signed distances from the origin. One can use the same principle to specify the position of any point in three-dimensional space by three Cartesian coordinates, its signed distances to three mutually perpendicular planes (or, equivalently, by its perpendicular projection onto three mutually perpendicular lines). In general, ''n'' Cartesian coordinates (an element of real ''n''-space) specify the point in an ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coprime Integers
In mathematics, two integers and are coprime, relatively prime or mutually prime if the only positive integer that is a divisor of both of them is 1. Consequently, any prime number that divides does not divide , and vice versa. This is equivalent to their greatest common divisor (GCD) being 1. One says also '' is prime to '' or '' is coprime with ''. The numbers 8 and 9 are coprime, despite the fact that neither considered individually is a prime number, since 1 is their only common divisor. On the other hand, 6 and 9 are not coprime, because they are both divisible by 3. The numerator and denominator of a reduced fraction are coprime, by definition. Notation and testing Standard notations for relatively prime integers and are: and . In their 1989 textbook ''Concrete Mathematics'', Ronald Graham, Donald Knuth, and Oren Patashnik proposed that the notation a\perp b be used to indicate that and are relatively prime and that the term "prime" be used instead of coprime (as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aide-toi, Le Ciel T'aidera
Aide-toi, le ciel t'aidera ( French idiom, meaning "God helps those who help themselves"; literally, "Help yourself, heaven shall help you"), simply called Aide-toi, was a French society that aimed to stir up the electorate against the government during the Bourbon Restoration (1814–1830). History The term "''Aide-toi, le ciel t'aidera''" began to be used by some political writers around 1824, and became the motto and title of the Aide-toi society. The purpose was to create opposition to the government by strictly legitimate means, mainly letters and political journals. The founders and active members were mostly from the Doctrinaires party, including François Guizot, who was president for some time, Tanneguy Duchâtel, Prosper Duvergier de Hauranne, Paul-François Dubois, Charles de Rémusat, Adolphe Thiers and Éléonore-Louis Godefroi Cavaignac. The association's organ was first ''Le Globe'' and then ''Le National''. Charles Renouard was among the liberals who opposed th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
