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Double Transposition
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] |
Cryptography
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 synonymo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Le Matin (France)
''Le Matin'' was a French daily newspaper first published in 1884 and discontinued in 1944. History ''Le Matin'' was launched on the initiative of Chamberlain & Co., a group of American financiers and the American newspaper editor Samuel Selwyn Chamberlain, in 1883, on the model of the British daily '' The Morning News''. The direction of the project was entrusted to the French journalist Alfred Edwards, who launched the first issue on 26 February 1884. His home was then situated in the 10th arrondissement of Paris, at 6 boulevard Poissonnière, and his offices at numbers 3 to 9 on the same street. A few months later, Edwards left ''Le Matin'' to found his own journal, ''Le Matin Français'', which soon surpassed the circulation of ''Le Matin''. Later Edwards bought ''Le Matin'' and merged the two papers. He modernized the resulting hybrid with the most modern techniques and technologies such as the telegraph, and signed great writers such as Jules Vallès and the député A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zodiac Killer
The Zodiac Killer is the pseudonym of an unidentified serial killer who operated in Northern California in the late 1960s. The case has been described as the most famous unsolved murder case in American history. It became a fixture of popular culture and inspired amateur detectives to attempt to solve it. The Zodiac murdered five known victims in the San Francisco Bay Area between December 1968 and October 1969, operating in rural, urban and suburban settings. He targeted young couples and a lone male cab driver. His known attacks took place in Benicia, Vallejo, unincorporated Napa County, and the city of San Francisco proper. Two of his wounded victims survived. The Zodiac claimed to have murdered 37 victims. He has been linked to several other cold cases, some in Southern California or outside the state. The Zodiac coined this name in a series of taunting letters and cards that he mailed to regional newspapers, in which he threatened killing sprees and bombings if they were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brute-force Attack
In cryptography, a brute-force attack consists of an attacker submitting many passwords or passphrases with the hope of eventually guessing correctly. The attacker systematically checks all possible passwords and passphrases until the correct one is found. Alternatively, the attacker can attempt to guess the key which is typically created from the password using a key derivation function. This is known as an exhaustive key search. A brute-force attack is a cryptanalytic attack that can, in theory, be used to attempt to decrypt any encrypted data (except for data encrypted in an information-theoretically secure manner). Such an attack might be used when it is not possible to take advantage of other weaknesses in an encryption system (if any exist) that would make the task easier. When password-guessing, this method is very fast when used to check all short passwords, but for longer passwords other methods such as the dictionary attack are used because a brute-force search ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Known-plaintext Attack
The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secret keys and code books. The term "crib" originated at Bletchley Park, the British World War II decryption operation, where it was defined as: History The usage "crib" was adapted from a slang term referring to cheating (e.g., "I cribbed my answer from your test paper"). A "crib" originally was a literal or interlinear translation of a foreign-language text—usually a Latin or Greek text—that students might be assigned to translate from the original language. The idea behind a crib is that cryptologists were looking at incomprehensible ciphertext, but if they had a clue about some word or phrase that might be expected to be in the ciphertext, they would have a "wedge," a test to break into it. If their otherwise random attacks on the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hill Climbing
numerical analysis, hill climbing is a mathematical optimization technique which belongs to the family of local search. It is an iterative algorithm that starts with an arbitrary solution to a problem, then attempts to find a better solution by making an incremental change to the solution. If the change produces a better solution, another incremental change is made to the new solution, and so on until no further improvements can be found. For example, hill climbing can be applied to the travelling salesman problem. It is easy to find an initial solution that visits all the cities but will likely be very poor compared to the optimal solution. The algorithm starts with such a solution and makes small improvements to it, such as switching the order in which two cities are visited. Eventually, a much shorter route is likely to be obtained. Hill climbing finds optimal solutions for convex problems – for other problems it will find only local optima (solutions that cannot be imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Algorithm
In computer science and operations research, a genetic algorithm (GA) is a metaheuristic inspired by the process of natural selection that belongs to the larger class of evolutionary algorithms (EA). Genetic algorithms are commonly used to generate high-quality solutions to optimization and search problems by relying on biologically inspired operators such as mutation, crossover and selection. Some examples of GA applications include optimizing decision trees for better performance, solving sudoku puzzles, hyperparameter optimization, etc. Methodology Optimization problems In a genetic algorithm, a population of candidate solutions (called individuals, creatures, organisms, or phenotypes) to an optimization problem is evolved toward better solutions. Each candidate solution has a set of properties (its chromosomes or genotype) which can be mutated and altered; traditionally, solutions are represented in binary as strings of 0s and 1s, but other encodings are also possible. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Distribution
In statistics, the frequency (or absolute frequency) of an event i is the number n_i of times the observation has occurred/recorded in an experiment or study. These frequencies are often depicted graphically or in tabular form. Types The cumulative frequency is the total of the absolute frequencies of all events at or below a certain point in an ordered list of events. The (or empirical probability) of an event is the absolute frequency normalized by the total number of events: : f_i = \frac = \frac. The values of f_i for all events i can be plotted to produce a frequency distribution. In the case when n_i = 0 for certain i, pseudocounts can be added. Depicting frequency distributions A frequency distribution shows us a summarized grouping of data divided into mutually exclusive classes and the number of occurrences in a class. It is a way of showing unorganized data notably to show results of an election, income of people for a certain region, sales of a product within ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptanalysis
Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown. In addition to mathematical analysis of cryptographic algorithms, cryptanalysis includes the study of side-channel attacks that do not target weaknesses in the cryptographic algorithms themselves, but instead exploit weaknesses in their implementation. Even though the goal has been the same, the methods and techniques of cryptanalysis have changed drastically through the history of cryptography, adapting to increasing cryptographic complexity, ranging from the pen-and-paper methods of the past, through machines like the British Bombes and Colossus computers at Bletchley Park in World War II, to the mathematically advanced comput ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rasterschlüssel 44
Rasterschlüssel 44 (abbr. RS 44) was a manual cipher system, used by the German Wehrmacht during the Second World War. The cipher was designed by the astronomer and sometime cryptographer Walter Fricke while working as a conscript in Section IIb, of Group 2 of OKW/Chi and introduced in March 1944 and the Allied forces codebreakers had considerable difficulties in breaking it. Cryptanalysis, if successful, generally required a 40 letter crib (known plaintext) and some two weeks, making the tactical information outdated before it could be exploited. The combination of strength and ease of use made RS 44 an ideal hand cipher. Design The cipher is a transposition based grille cipher, consisting of a grid with 25 columns and 24 rows. Each row contains 10 randomly placed white cells (to be filled with text) and 15 black cells. The columns are labeled with shuffled digraphs and numbers and the rows with digraphs. The key sheet also contains two letter substitution alphabets to enc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VIC Cipher
Vic (; es, Vic or Pancracio Celdrán (2004). Diccionario de topónimos españoles y sus gentilicios (5ª edición). Madrid: Espasa Calpe. p. 843. ISBN 978-84-670-3054-9. «Vic o Vich (viquense, vigitano, vigatán, ausense, ausetano, ausonense): Ciudad barcelonesa, cabeza del partido judicial situada cerca de los ríos Ter y Méder, en la Plana de Vich.») is the capital of the ''comarca'' of Osona, in the province of Barcelona, Catalonia, Spain. Vic is located from Barcelona and from Girona. Geography Vic lies in the middle of the Plain of Vic, equidistant from Barcelona and the Pyrenees. Vic has persistent fog in winter as a result of a thermal inversion, with temperatures as low as -10 °C, an absolute record of -24 °C and episodes of cold and severe snowstorms. For this reason the natural vegetation includes the pubescent oak typical of the sub-Mediterranean climates of eastern France, Northern Italy and the Balkans. Names Originally known as ''Auso'', it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Office Of Strategic Services
The Office of Strategic Services (OSS) was the intelligence agency of the United States during World War II. The OSS was formed as an agency of the Joint Chiefs of Staff (JCS) to coordinate espionage activities behind enemy lines for all branches of the United States Armed Forces. Other OSS functions included the use of propaganda, subversion, and post-war planning. The OSS was dissolved a month after the end of the war. Intelligence tasks were shortly later resumed and carried over by its successors the Department of State's Bureau of Intelligence and Research (INR), and the independent Central Intelligence Agency (CIA). On December 14, 2016, the organization was collectively honored with a Congressional Gold Medal. Origin Prior to the formation of the OSS, the various departments of the executive branch, including the State, Treasury, Navy, and War Departments conducted American intelligence activities on an ''ad hoc'' basis, with no overall direction, coordination, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
