FACTOID # 19: Cheap sloppy joes: Looking for reduced-price lunches for schoolchildren? Head for Oklahoma!
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Substitution cipher

In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; 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 an inverse substitution. The German Lorenz cipher machine Cryptography or cryptology is a field of mathematics and computer science concerned with information security and related issues, particularly encryption and authentication. ... In cryptography, encryption is the process of obscuring information to make it unreadable without special knowledge. ... This article is about algorithms for encryption and decryption. ...


Substitution ciphers can be compared with transposition ciphers. In a transposition cipher, 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. In classical cryptography, a transposition cipher changes one character from the plaintext to another (to decrypt the reverse is done). ...


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 is termed polygraphic. A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different times in the message—such as with homophones, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext.

Contents


Simple substitution

ROT13 is a Caesar cipher, a type of substitution cipher. In ROT13, the alphabet is rotated 13 steps.
ROT13 is a Caesar cipher, a type of substitution cipher. In ROT13, the alphabet is rotated 13 steps.

Substitution over a single letter—simple substitution—can be demonstrated by writing out the alphabet in some order to represent the substitution. This is termed a substitution alphabet. The cipher alphabet may be shifted or reversed (creating the Caesar and Atbash ciphers, respectively) or scrambled in a more complex fashion, in which case it is called a mixed alphabet or deranged alphabet. Traditionally, mixed alphabets are created by first writing out a keyword, then all the remaining letters. Download high resolution version (820x515, 77 KB)ROT13 diagram, original for Wikipedia, made in Dia. ... Download high resolution version (820x515, 77 KB)ROT13 diagram, original for Wikipedia, made in Dia. ... ROT13 replaces each letter by its partner 13 characters further along the alphabet. ... The action of a Caesar cipher is to move each letter a number of places down the alphabet. ... The action of a Caesar cipher is to move each letter a number of places down the alphabet. ... Atbash is a simple substitution cipher for the Hebrew alphabet. ...


Examples

Using this system, the keyword "zebras" gives us the following alphabets:

Plaintext alphabet: abcdefghijklmnopqrstuvwxyz
Ciphertext alphabet: ZEBRASCDFGHIJKLMNOPQTUVWXY

A message of

 flee at once. we are discovered! 

enciphers to

 SIAA ZQ LKBA. VA ZOA RFPBLUAOAR! 

Traditionally, the ciphertext is written out in blocks of fixed length, omitting punctuation and spaces; this is done to help avoid transmission errors and to disguise word boundaries from the plaintext. These blocks are called "groups", and sometimes a "group count" (i.e., the number of groups) is given as an additional check. Five letter groups are traditional, dating from when messages used to be transmitted by telegraph: The plain text term has a different meaning. ... It has been suggested that Electrical telegraph be merged into this article or section. ...

 SIAAZ QLKBA VAZOA RFPBL UAOAR 

If the length of the message happens not to be divisible by five, it may be padded at the end with "nulls". These can be any characters that decrypt to obvious nonsense, so the receiver can easily spot them and discard them. KK Null, a Japanese musician Null, a special value in computer programming. ...


The ciphertext alphabet is sometimes different from the plaintext alphabet; for example, in the pigpen cipher, the ciphertext consists of a set of symbols derived from a grid. For example: The Pigpen Cipher is a simple substitution cipher exchanging letters for symbols, using a grid. ...

An example pigpen message

Such features make little difference to the security of a scheme, however — at the very least, any set of strange symbols can be transcribed back into an A-Z alphabet and dealt with as normal. Image File history File links Download high resolution version (1024x158, 25 KB)A sample pigpen cipher message. ...


Security for simple substitution ciphers

A disadvantage of this method of derangement is that the last letters of the alphabet (which are mostly low frequency) tend to stay at the end. A stronger way of constructing a mixed alphabet is to perform a columnar transposition on the ordinary alphabet using the keyword, but this is not often done. In classical cryptography, a transposition cipher changes one character from the plaintext to another (to decrypt the reverse is done). ...


Although the number of possible keys is very large (26! approx 2^{88.4}, or about 88 bits), this cipher is not very strong, being easily broken. Provided the message is of reasonable length (see below), the cryptanalyst can deduce the probable meaning of the most common symbols by analysing the frequency distribution of the ciphertext—frequency analysis. This allows formation of partial words, which can be tentatively filled in, progressively expanding the (partial) solution (see frequency analysis for a demonstration of this). In some cases, underlying words can also be determined from the pattern of their letters; for example, attract, osseous, and words with those two as the root are the only common English words with the pattern ABBCADB. Many people solve such ciphers for recreation, as with cryptogram puzzles in the newspaper. A key is a piece of information that controls the operation of a cryptography algorithm. ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ... In statistics, a frequency distribution is a list of the values that a variable takes in a sample. ... In mathematics, physics and signal processing, frequency analysis is a method to decompose a function, wave, or signal into its frequency components so that it is possible to have the frequency spectrum. ... In mathematics, physics and signal processing, frequency analysis is a method to decompose a function, wave, or signal into its frequency components so that it is possible to have the frequency spectrum. ... The English language is a West Germanic language that originates in England. ... A cryptogram is a short piece of text encrypted with a simple substitution cipher in which each letter is replaced by a different letter. ...


According to the unicity distance of English, 27.6 letters of ciphertext are required to crack a mixed alphabet simple substitution. In practice, typically about 50 letters are needed, although some messages can be broken with fewer if unusual patterns are found. In other cases, the plaintext can be contrived to have a nearly flat frequency distribution, and much longer plaintexts will then be required. Unicity distance is a term used in cryptography referring to the length of an original ciphertext needed to break the cipher by reducing the number of possible spurious keys to zero in a brute force attack. ... The English language is a West Germanic language that originates in England. ...


Homophonic substitution

The forged nomenclator message used in the Babington Plot.
The forged nomenclator message used in the Babington Plot.

An early attempt to increase the difficulty of frequency analysis attacks on substitution ciphers was to disguise plaintext letter frequencies by homophony. In these ciphers, plaintext letters map to more than one ciphertext symbol. Usually, the highest-frequency plaintext symbols are given more equivalents than lower frequency letters. In this way, the frequency distribution is flattened, making analysis more difficult. Image File history File links Download high resolution version (575x740, 112 KB)Thomas Phelippes forged cipher postscript to Mary, Queen of Scots letter to Anthony Babington, sourced from UK National Archives article on Mary. ... Image File history File links Download high resolution version (575x740, 112 KB)Thomas Phelippes forged cipher postscript to Mary, Queen of Scots letter to Anthony Babington, sourced from UK National Archives article on Mary. ... Walsinghams Decypherer forged this cipher postscript to Marys letter to Babington. ...


Since more than 26 characters will be required in the ciphertext alphabet, various solutions are employed to invent larger alphabets. Perhaps the simplest is to use a numeric substitution 'alphabet'. Another method consists of simple variations on the existing alphabet; uppercase, lowercase, upside down, etc. More artistically, though not necessarily more securely, some homophonic ciphers employed wholly invented alphabets of fanciful symbols. (See Poe's The Gold Bug for a literary example; cf. the Voynich manuscript.) Edgar Allan Poe (January 19, 1809 – October 7, 1849) was an American poet, short story writer, editor, critic and one of the leaders of the American Romantic Movement. ... The Gold Bug is a short story by Edgar Allan Poe. ... The Voynich manuscript is written in an unknown script. ...


An interesting variant is the nomenclator. Named after the public official who announced the titles of visiting dignitaries, this cipher combined a small codebook with large homophonic substitution tables. Originally the code was restricted to the names of important people, hence the name of the cipher; in later years it covered many common words and place names as well. The symbols for whole words (codewords in modern parlance) and letters (cipher in modern parlance) were not distinguished in the ciphertext. The Rossignols' Great Cypher used by Louis XIV of France was one; after it went out of use, messages in French archives were unbreakable for several hundred years. Categories: Cryptography stubs | Cryptography ... In the context of cryptography, a code is a method used to transform a message into an obscured form, preventing those not in on the secret from understanding what is actually transmitted. ... In telecommunication, the term code word has the following meanings: A cryptonym used to identify sensitive intelligence data. ... This article is about algorithms for encryption and decryption. ... Antoine Rossignol, Maistre des Comptes. ... In the history of cryptography, the Great Cipher was a nomenclator cipher developed by the Rossignols, several generations of whom served the French Crown as cryptographers. ... Louis XIV (Louis - Dieu donné) or (Louis - God given) (September 5, 1638 – September 1, 1715), reigned as King of France and of Navarre from May 14, 1643 until his death at the age of 77. ... For other uses of the word Archive, see Archive (disambiguation) Archives refers to a collection of records, and also refers to the location in which these records are kept. ...


Nomenclators were the standard fare of diplomatic correspondence, espionage, and advanced political conspiracy from the early fifteenth century to the late eighteenth century; most conspirators were and have remained less cryptographically sophisticated. Although government intelligence cryptanalysts were systematically breaking nomenclators by the mid-sixteenth century, and superior systems had been available since 1467, the usual response to cryptanalysis was simply to make the tables larger. By the late eighteenth century, when the system was beginning to die out, some nomenclators had 50,000 symbols. The United Nations, with its headquarters in New York City, is the largest international diplomatic organization. ... Espionage is the practice of obtaining information about an organization or a society that is considered secret or confidential (spying) without the permission of the holder of the information. ... In a political sense, conspiracy refers to a group of persons united in the goal of usurping or overthrowing an established political power. ... (14th century - 15th century - 16th century - other centuries) As a means of recording the passage of time, the 15th century was that century which lasted from 1401 to 1500. ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... An intelligence agency is a governmental organization devoted to gathering of information by means of espionage, communication interception, cryptanalysis, cooperation with other institutions, and evaluation of public sources. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information without access to the secret information which is normally required to do so. ... (15th century - 16th century - 17th century - more centuries) As a means of recording the passage of time, the 16th century was that century which lasted from 1501 to 1600. ... Events October 29 - Battle of Brusthem: Charles the Bold defeats Liege Beginning of the Sengoku Period in Japan. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ...


Nevertheless, not all nomenclators were broken; today, cryptanalysis of archived ciphertexts remains a fruitful area of historical research. For other senses of this word, see history (disambiguation). ...


The book cipher and straddling checkerboard are types of homophonic cipher. A book cipher is a cipher in which the key is the identity of a book. ... In cryptography, a straddling checkerboard is a device for converting an alphabetic plaintext into digits whilst simultaneously achieving fractionation (a simple form of information diffusion) and homophony (a simple method for suppressing peaks of the frequency distribution). ...


Polyalphabetic substitution

Main article: Polyalphabetic cipher

Polyalphabetic substitution ciphers were first described in 1467 by Leone Battista Alberti in the form of disks. Johannes Trithemius, in his book Steganographia (Ancient Greek for "hidden writing") introduced the now more standard form of a tableau (see below; ca. 1500 but not published until much later). A more sophisticated version using mixed alphabets was described in 1563 by Giovanni Battista della Porta in his book, De Furtivis Literarum Notis (Latin for "On concealed characters in writing"). A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets. ... Events October 29 - Battle of Brusthem: Charles the Bold defeats Liege Beginning of the Sengoku Period in Japan. ... Statue of Leon Battista Alberti. ... Polygraphia (1518) — the first printed book on cryptography. ... Note: This article contains special characters. ... 1500 was a common year starting on Monday (see link for calendar) of the Gregorian calendar. ... Events February 1 - Sarsa Dengel succeeds his father Menas as Emperor of Ethiopia February 18 - The Duke of Guise is assassinated while besieging Orléans March - Peace of Amboise. ... Giambattista della Porta. ... Latin is an ancient Indo-European language originally spoken in the region around Rome called Latium. ...


In a polyalphabetic cipher, multiple cipher alphabets are used. To facilitate encryption, all the alphabets are usually written out in a large table, traditionally called a tableau. The tableau is usually 26×26, so that 26 full ciphertext alphabets are available. The method of filling the tableau, and of choosing which alphabet to use next, defines the particular polyalphabetic cipher. All such ciphers are easier to break than once believed, as substitution alphabets are repeated for sufficiently large plaintexts. A table is a mode of visual communication that maps the logical structure of a set of data into a hierarchical matrix. ...


One of the most popular was that of Blaise de Vigenère. First published in 1585, it was considered unbreakable until 1863, and indeed was commonly called le chiffre indéchiffrable (French for "indecipherable cipher"). Blaise de Vigenère (April 5, 1523 - 1596) was a French diplomat and cryptographer. ... 1585 was a common year starting on Tuesday of the Gregorian calendar or a common year starting on Friday of the Julian calendar. ... 1863 (MDCCCLXIII) is a common year starting on Thursday of the Gregorian calendar (or a common year starting on Saturday of the Julian calendar). ...


In the Vigenère cipher, the first row of the tableau is filled out with a copy of the plaintext alphabet, and successive rows are simply shifted one place to the left. (Such a simple tableau is called a tabula recta, and mathematically corresponds to adding the plaintext and key letters, modulo 26.) A keyword is then used to choose which ciphertext alphabet to use. Each letter of the keyword is used in turn, and then they are repeated again from the beginning. So if the keyword is 'CAT', the first letter of plaintext is enciphered under alphabet 'C', the second under 'A', the third under 'T', the fourth under 'C' again, and so on. In practice, Vigenère keys were often phrases several words long. The Vigenère cipher is named for Blaise de Vigenère (pictured), although Giovan Batista Belaso had invented the cipher earlier. ... Tabula recta In cryptography, the tabula recta is a square table of alphabets, each one made by shifting the previous one to the left. ... Modular arithmetic (sometimes called modulo arithmetic) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ...


In 1863, Friedrich Kasiski published a method (probably discovered secretly and independently before the Crimean War by Charles Babbage) which enabled the calculation of the length of the keyword in a Vigenère ciphered message. Once this was done, ciphertext letters that had been enciphered under the same alphabet could be picked out and attacked separately as a number of semi-independent simple substitutions - complicated by the fact that within one alphabet letters were separated and did not form complete words, but simplified by the fact that usually a tabula recta had been employed. 1863 (MDCCCLXIII) is a common year starting on Thursday of the Gregorian calendar (or a common year starting on Saturday of the Julian calendar). ... Major Friedrich Wilhelm Kasiski (29 November 1805–22 May 1881) was a Prussian infantry officer, cryptographer and archeologist. ... Combatants United Kingdom of Great Britain and Ireland, Second French Empire, Ottoman Empire, Kingdom of Sardinia Imperial Russia Strength 250,000 British 400,000 French 10,000 Sardinian 1,200,000 Russian Casualties 17,500 British 90,000 French 35,000 Turkish 2,050 Sardinian killed, wounded and died of... Charles Babbage Charles Babbage (26 December 1791 – 18 October 1871) was an English mathematician, analytical philosopher, mechanical engineer and (proto-) computer scientist who originated the idea of a programmable computer. ...


As such, even today a Vigenère type cipher should theoretically be difficult to break if mixed alphabets are used in the tableau, if the keyword is random, and if the total length of ciphertext is less than 27.6 times the length of the keyword. These requirements are rarely understood in practice, and so Vigenère enciphered message security is usually less than might have been.


Other notable polyalphabetics include:

  • The Gronsfeld cipher. This is identical to the Vigenère except that only 10 alphabets are used, and so the "keyword" is numerical.
  • The Beaufort cipher. This is practically the same as the Vigenère, except the tabula recta is replaced by a backwards one, mathematically equivalent to ciphertext = key - plaintext. This operation is self-inverse, so that exactly the same table is used in exactly the same way, for both encryption and decryption.
  • The autokey cipher, which mixes plaintext in to the keying to avoid periodicity in the key.
  • The running key cipher, where the key is made very long by using a passage from a book or similar text.

Modern stream ciphers can also be seen, from a sufficiently abstract perspective, to be a form of polyalphabetic cipher in which all the effort has gone into making the keystream as long and unpredictable as possible. The Beaufort cipher, created by Sir Francis Beaufort, is a cipher that is similar to the Vigenère cipher but uses a slightly modified enciphering mechanism and tableau. ... An autokey cipher, or self-synchronizing stream cipher, is a cipher which incorporates the message (the plaintext) into the key. ... In mathematics, a periodic function is a function that repeats its values after some definite period has been added to its independent variable. ... In classical cryptography, the runnning key cipher is a type of polyalphabetic substitution cipher in which a text, typically from a book, is used to provide a very long key stream. ... The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ...


Polygraphic substitution

In a polygraphic substitution cipher, plaintext letters are substituted for in larger groups (typically pairs, making a digraphic cipher), instead of substituting letters individually. The advantage of this is first that the frequency distribution of digraphs is much flatter than that of individual letters (though not actually flat in real languages; for example, 'TH' is much more common than 'XQ' in English). Second, the larger number of symbols requires correspondingly more ciphertext to productively analyse letter frequencies.


Because 262 = 676, to substitute pairs with a substitution alphabet would take an alphabet 676 symbols long—which would be rather cumbersome. (Actually, not every combination would need to be created, or rare combinations could be split into individual letters, but this is negligible.) In the same De Furtivis Literarum Notis mentioned above, della Porta actually proposed such a system, with a 20 x 20 tableau (for the 20 letters of the Italian/Latin alphabet he was using) filled with 400 unique glyphs. However the system was impractical and probably never actually used. Algebraic or geometric methods are typically used to construct the substitution from simple operations. These are the astrological glyphs as most commonly used in Western Astrology A glyph is a specific symbol representing a semantic or phonetic unit of definitive value in a writing system. ... Linear algebra lecture at Helsinki University of Technology This article is about the branch of mathematics; for other uses of the term see algebra (disambiguation). ... Table of Geometry, from the 1728 Cyclopaedia. ...


The earliest practical digraphic substitution was the so-called Playfair cipher, actually invented by Sir Charles Wheatstone in 1854. It was in military use from the Boer War through World War II. In this cipher, a 5 x 5 grid is filled with the letters of a mixed alphabet (two letters, usually I and J, are combined). A digraphic substitution is then simulated by taking pairs of letters as two corners of a rectangle, and using the other two corners as the ciphertext (see the Playfair cipher main article for a diagram). Special rules handle double letters and pairs falling in the same row or column. The Playfair system was invented by Charles Wheatstone, who first described it in 1854. ... Charles Wheatstone Sir Charles Wheatstone (February 6, 1802 - October 19, 1875) was the British inventor of many innovations including the English concertina the Stereoscope an early form of microphone the Playfair cipher (named for Lord Playfair, the person who publicized it) He was a major figure in the development of... 1854 was a common year starting on Sunday (see link for calendar). ... Combatants British Empire Orange Free State, South African Republic Commanders Frederick Roberts later Lord Kitchener Christiaan Rudolf de Wet and Paul Kruger Casualties Military dead:22,000 Civilian dead:N/A Total dead:22,000 Military dead:6,500 Civilian dead:24,000 Total dead:30,500 The Second Boer... Combatants Allies: Poland, British Commonwealth, France/Free France, Soviet Union, United States, China, and others Axis Powers: Germany, Italy, Japan, and others Casualties Military dead: 17 million Civilian dead: 33 million Total dead: 50 million Military dead: 8 million Civilian dead: 4 million Total dead: 12 million World War II... The Playfair system was invented by Charles Wheatstone, who first described it in 1854. ...


Several other practical polygraphics were introduced in 1901 by Felix Delastelle, including the bifid and four-square ciphers (both digraphic) and the trifid cipher (probably the first practical trigraphic). Felix Marie Delastelle (1840–1902) was a Frenchman most famous for his invention of several systems of polygraphic substitution ciphers including the bifid, trifid, and the four-square ciphers. ... In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion. ... The Four-square cipher is a manual symmetric encryption technique. ... In classical cryptography, the trifid cipher is a cipher invented around 1901 by Felix Delastelle, which extends the concept of the bifid cipher to a third dimension, allowing each symbol to be fractionated into 3 elements instead of two. ...


The Hill cipher is a polygraphic substitution which can combine much larger groups of letters simultaneously, using linear algebra. It was invented in 1929 by Lester S. Hill. Each letter is treated as a digit in base 26: A = 0, B =1, and so on. (In a variation, 3 extra symbols are added to make the basis prime.) A block of n letters is then considered as a vector of n dimensions, and multiplied by a n x n matrix, modulo 26. The components of the matrix are the key, and should be random provided that the matrix is invertible in mathbb{Z}_{26}^n (to ensure decryption is possible). Astonishingly, a Hill cipher of dimension 6 was once implemented mechanically! Hills cipher machine, from figure 4 of the patent In classical cryptography, the Hill cipher is a polygraphic substitution cipher based on linear algebra. ... Linear algebra is the branch of mathematics concerned with the study of vectors, vector spaces (also called linear spaces), linear transformations, and systems of linear equations in finite dimensions. ... 1929 (MCMXXIX) was a common year starting on Tuesday (link will take you to calendar). ... A numeral is a symbol or group of symbols that represents a number. ... In linear algebra, a basis is a minimum set of vectors that, when combined, can address every vector in a given space. ... In mathematics, a prime number (or a prime) is a natural number that has exactly two (distinct) natural number divisors, which are 1 and the prime number itself. ... Vector spaces (or linear spaces) are spaces whose elements, known as vectors, can be scaled and added; all linear combinations can be formed. ... 2-dimensional renderings (ie. ... In mathematics, a matrix (plural matrices) is a rectangular table of numbers or, more generally, a table consisting of abstract quantities that can be added and multiplied. ... Modular arithmetic (sometimes called modulo arithmetic) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ... In ordinary language, the word random is used to express apparent lack of purpose or cause. ...


Unfortunately, the Hill cipher is vulnerable to a known-plaintext attack because it is completely linear, so it must be combined with some non-linear step to defeat this attack. The combination of wider and wider weak, linear diffusive steps like a Hill cipher, with non-linear substitution steps, ultimately leads to a substitution-permutation network (e.g., a Feistel cipher), so it is possible—from this extreme perspective—to consider modern block ciphers as a type of polygraphic substitution. The known-plaintext attack (KPA) is an attack model for cryptanalytic where the attacker has samples of both the plaintext and its encrypted version (ciphertext) and is at liberty to make use of them to reveal further secret information; typically this is the secret key. ... The word linear comes from the Latin word linearis, which means created by lines. ... To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ... In cryptography, confusion and diffusion are two properties of the operation of a secure cipher which were identified by Shannon in his paper, Communication Theory of Secrecy Systems published in 1949. ... In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES. These networks consist of S-boxes and P-boxes that transform blocks of input bits into output bits. ... Feistel cipher - Wikipedia /**/ @import /skins-1. ... Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ...


Mechanical substitution ciphers

Between circa WWI and the widespread availability of computers (for some governments this was approximately the 1950s or 1960s; for other organizations it was a decade or more later; for individuals it was no earlier than 1975), mechanical implementations of polyalphabetic substitution ciphers were widely used. Several inventors had similar ideas about the same time, and rotor cipher machines were patented four times in 1919. The most important of the resulting machines was the Enigma, especially in the versions used by the German military from approximately 1930. The Allies also developed and used rotor machines (eg, SIGABA and Typex). WWI may be an acronym for: World War I World Wrestling Industry This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... The IBM ThinkCentre A Series is a popular line of computers. ... The 1950s were the decade that spanned the years 1950 through 1959, although some sources say from 1951 through 1960. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... 1975 (MCMLXXV) was a common year starting on Wednesday (the link is to a full 1975 calendar). ... In cryptography, a rotor machine is a electro-mechanical device used for encrypting and decrypting secret messages. ... 1919 (MCMXIX) was a common year starting on Wednesday (see link for calendar). ... A three-rotor German military Enigma machine showing, from bottom to top, the plugboard, the keyboard, the lamps and the finger-wheels of the rotors emerging from the inner lid (version with labels). ... German cavalry and motorized units entering Poland from East Prussia during the Polish Campaign of 1939 Wehrmacht (Defence force) was the name of the armed forces of Germany from 1935 to 1945. ... 1930 (MCMXXX) is a common year starting on Wednesday. ... When spelt with a capital A, Allies usually denotes the countries supporting the Triple Entente who fought together against the Central Powers in World War I and against the Axis Powers in World War II. For more information, see the related articles: Allies of World War I and Allies of... SIGABA In the history of cryptography, the ECM Mark II was a rotor machine used by the United States from World War II (WWII) until the 1950s. ... Typex was based on the commercial Enigma machine, but incorporated a number of additional features to improve the security. ...


All of these were similar in that the substituted letter was chosen electrically from amongst the huge number of possible combinations resulting from the rotation of several letter disks. Since one or more of the disk rotated mechanically with each plaintext letter enciphered, the number of alphabets used was substantially more than astronomical. Early versions of these machine were, nevertheless, breakable. William F. Friedman of the US Army's SIS early found vulnerabilities in Hebern's rotor machine, and GC&CS's Dillwyn Knox solved versions of the Enigma machine (those without the "plugboard") well before WWII began. Traffic protected by essentially all of the German military Enigmas was broken by Allied cryptanalysts, most notably those at Bletchley Park, beginning with the German Army variant used in the early 1930s. This version was broken by inspired mathematical insight by Marian Rejewski in Poland. The article on electrical energy is located elsewhere. ... William Friedman. ... SiS is also an abbreviation for Silicon Integrated Systems Note that both S letters are capital. ... A single-rotor Hebern machine. ... The Government Communications Headquarters (GCHQ) (previously named the Government Code and Cipher School (GC&CS)) is the main British intelligence service providing signals intelligence (SIGINT). ... Alfred Dillwyn Dilly Knox (23 July 1884 – 27 February 1943) was a British codebreaker and classical scholar at Kings College, Cambridge. ... Combatants Allies: Poland, British Commonwealth, France/Free France, Soviet Union, United States, China, and others Axis Powers: Germany, Italy, Japan, and others Casualties Military dead: 17 million Civilian dead: 33 million Total dead: 50 million Military dead: 8 million Civilian dead: 4 million Total dead: 12 million World War II... During World War II, British and American cryptographers at Bletchley Park broke a large number of Axis codes and ciphers, including the German Enigma machine. ... Marian Rejewski (probably 1932, the year he first solved the Enigma machine). ...


No messages protected by the SIGABA and Typex machines were ever, so far as is publicly known, broken. SIGABA In the history of cryptography, the ECM Mark II was a rotor machine used by the United States from World War II (WWII) until the 1950s. ... Typex was based on the commercial Enigma machine, but incorporated a number of additional features to improve the security. ...


The one-time pad

Main article: One-time pad

One type of substitution cipher, the one-time pad, is quite special. It was invented near the end of WWI by Gilbert Vernam and Joseph Mauborgne in the US. It was mathematically proved unbreakable by Claude Shannon, probably during WWII; his work was first published in the late 1940s. In its most common implementation, the one-time pad can be called a substitution cipher only from an unusual perspective; typically, the plaintext letter is combined (not substituted) in some manner (eg, XOR) with the key material character at that position. Excerpt from a one-time pad. ... Excerpt from a one-time pad. ... Gilbert Sandford Vernam (1890–7 February 1960) was a AT&T Bell Labs engineer who, in 1917, invented the stream cipher and later co-invented the one-time pad cipher. ... In the history of cryptography, Joseph Oswald Mauborgne (1881–1971) co-invented the one-time pad with Gilbert Vernam of Bell Labs. ... Claude Elwood Shannon (April 30, 1916 _ February 24, 2001) has been called the father of information theory, and was the founder of practical digital circuit design theory. ... // Events and trends World War II was a truly global conflict with many facets: immense human suffering, fierce indoctrination, and the use of new, extremely devastating weapons such as the atomic bomb. ... Exclusive disjunction (usual symbol xor) is a logical operator that results in true if one of the operands (not both) is true. ...


The one-time pad is, in most cases, impractical as it requires that the key material be as long as the plaintext, actually random, used once and only once, and kept entirely secret from all except the sender and intended receiver. When these conditions are violated, even marginally, the one-time pad is no longer unbreakable. Soviet one-time pad messages sent from the US for a brief time during WWII used non-random key material. US cryptanalysts, beginning in the late 40s, were able to, entirely or partially, break a few thousand messages out of several hundred thousand. (See VENONA) In ordinary language, the word random is used to express apparent lack of purpose or cause. ... State motto (Russian): Пролетарии всех стран, соединяйтесь! (Transliterated: Proletarii vsekh stran, soedinyaytes!) (Translated: Workers of the world, unite!) Capital Moscow Official language None; Russian (de facto) Government Federation of Soviet republics Area  - Total  - % water 1st before collapse 22,402,200 km² Approx. ... The VENONA project was a long-running and highly secret collaboration between the United States intelligence agencies and the United Kingdoms MI5 that involved the cryptanalysis of Soviet messages. ...


In a mechanical implementation, rather like the ROCKEX equipment, the one-time pad was used for messages sent on the Moscow-Washington hot line established after the Cuban missile crisis. Rockex, or Telekrypton, was an offline one-time tape cipher machine known to have been used by Britain and Canada from 1943. ... Government Russia District Subdivision Russia Central Federal District Federal City Mayor Yuri Luzhkov Geographical characteristics Area  - City 1,081 km² Population  - City (2005)    - Density 10,415,400   8537. ... Flag Seal Nickname: the District Motto: Justitia Omnibus (Justice for All) Location Location of Washington, D.C., with regard to the surrounding states of Maryland and Virginia. ... U.S.A.F. spy photo of one of the suspected launch sites The Cuban Missile Crisis was a confrontation during the Cold War between the Soviet Union and the russia regarding the Soviet deployment of nuclear missiles in Cuba. ...


Substitution in modern cryptography

Substitution ciphers as discussed above, especially the older pencil-and-paper hand ciphers, are no longer in serious use. However, the cryptographic concept of substitution carries on even today. From a sufficiently abstract perspective, modern bit-oriented block ciphers (eg, DES, or AES) can be viewed as substitution ciphers on an enormously large binary alphabet. In addition, block ciphers often include smaller substitution tables called S-boxes. See also substitution-permutation network. Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ... General Designer(s) IBM First published 1975 (January 1977 as the standard) Derived from Lucifer (cipher) Cipher(s) based on this design Triple DES, G-DES, DES-X, LOKI89, ICE Algorithm detail Block size(s) 64 bits Key size(s) 56 bits Structure Feistel network Number of rounds 16 Best... General Designer(s) Vincent Rijmen and Joan Daemen First published 1998 Derived from Square (cipher) Cipher(s) based on this design Crypton (cypher), Anubis (cipher), GRAND CRU Algorithm detail Block size(s) 128 bits note Key size(s) 128, 192 or 256 bits note Structure Substitution-permutation network Number of... The binary numeral system (base 2 numerals) represents numeric values using two symbols, typically 0 and 1. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ... In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES. These networks consist of S-boxes and P-boxes that transform blocks of input bits into output bits. ...


See also

The Vigenère cipher is named for Blaise de Vigenère (pictured), although Giovan Batista Belaso had invented the cipher earlier. ... ...

External links

  • Online simple substitution implementation (Flash)


Classical cryptography edit
Ciphers: ADFGVX | Affine | Atbash | Autokey | Bifid | Book | Caesar | Four-square | Hill | Nihilist | Permutation | Pigpen | Playfair | Polyalphabetic | Reihenschieber | Reservehandverfahren | Running key | Substitution | Transposition | Trifid | Two-square | Vigenère
Cryptanalysis: Frequency analysis | Index of coincidence
Misc: Cryptogram | Polybius square | Scytale | Straddling checkerboard | Tabula recta

  Results from FactBites:
 
Substitution Cipher (254 words)
Wiki says: In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth.
The cipher alphabet may be shifted or reversed (creating the Caesar and Atbash ciphers, respectively) or scrambled in a more complex fashion, in which case it is called a mixed alphabet or deranged alphabet.
It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions further down the alphabet.
The Knights Templar | Baphomet: The Atbash Cipher Theory | www.templarhistory.com (455 words)
In order to understand the Atbash Cipher theory, as it relates to the Baphomet mythos, it is first important to examine the origins of the code.
In the case of the Atbash cipher, the first letter of the alphabet is substituted for the last, the second for the second last and so on.
Whether the Templars were devoted to the goddess or simply respectful of wisdom, it cannot be argued that Schonfield's Atbash cipher theory is among the most plausible explanations of the etymology of Baphomet.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m