cahya/wikipedia-simple-en huggingface dataset:
Twofish

In cryptography, Twofish is a symmetric key block cipher with a block size of 128 bits and key lengths up to 256 bits. 

In 1997, the NIST announced for competition to choose a successor to DES to be known as AES, Twofish was one of the five finalists of the Advanced Encryption Standard competition, but was not selected as a standard. 

Twofish is related to the earlier block cipher Blowfish. Twofish's main features are the use of pre-computed key-dependent S-boxes, and a relatively complex key schedule. One half of an n-bit key is used as the actual encryption key and the other half of the n-bit key is used to modify the encryption algorithm (key-dependent S-boxes). Twofish uses some elements from other designs; for example, the pseudo-Hadamard transform (PHT) from the SAFER family of ciphers. Twofish uses the same Feistel structure as the DES.

On most software platforms Twofish is slightly slower than Rijndael (the chosen algorithm for Advanced Encryption Standard) for 128-bit keys, but somewhat faster for 256-bit keys.

Creators 
Twofish was designed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris Hall, and  Niels Ferguson; the "extended Twofish team" who met to made further cryptanalysis of Twofish and other AES competitors included Stefan Lucks, Tadayoshi Kohno, and Mike Stay.

Twofish algorithm is free for anyone to use without any restrictions whatsoever. The Twofish cipher has not been patented and the software example of its specification has been placed in the public domain. However, Twofish is not widely used like the Blowfish, which has been available for a longer period of time.

Cryptanalysis 
As of 2008, the best published cryptanalysis on the Twofish block cipher is a truncated differential cryptanalysis of the full 16-round version. The paper claims that the probability of truncated differentials attacks is 2-57.3 per block and that it will take about 251 chosen plaintexts (32 PiB worth of data) to find a good pair of truncated differentials.

Bruce Schneier responds in a 2005 blog entry that this paper does not present a full cryptanalytic attack, but only some hypothesized differential characteristics: "But even from a theoretical perspective, Twofish is not even remotely broken. There have been no extensions to these results since they were published" in 2000.

Related pages
 Blowfish (cipher)
 Advanced Encryption Standard
 Data Encryption Standard

References

Additional reading

Other websites 
 Twofish web page with full specifications, free source code, and other Twofish resources.
 David Wagner's sci.crypt post recommending AES over Twofish  — Wagner was one of the designers of Twofish.
 SCAN's entry for Twofish
  List of products using TwoFish

Cryptography
Truncated differential cryptanalysis

In cryptography, truncated differential cryptanalysis is a generalization of differential cryptanalysis, an attack model against block ciphers. In 1994 Lars Knudsen designed the technique, during this period ordinary differential cryptanalysis analyzes the full difference between two texts, the truncated version considers differences that are only determined to some extent. It has been applied to SAFER, IDEA, Skipjack, E2, Twofish, Camellia, CRYPTON, and the stream cipher Salsa20 as well.

References
 
 
  
  
  
 
 

Cryptography
Fatimid Caliphate

The Fatimid Caliphate was ruled by the al-Fātimiyyūn () dynasty  from 5 January 909 to 1171. It was an Arab Shi'a dynasty It ruled the fourth and final Arab caliphate. In different times different areas of the Maghreb, Egypt, and the Levant belonged to the caliphate.

Egyptian city of Cairo was made the capital. The term Fatimite is sometimes used to refer to the citizens of this caliphate as well. The ruling elite belonged to the Ismaili branch of Shi'ism. The leaders were also Shia Ismaili Imams. They had a religious significance to Ismaili Muslims. They are also part of the chain of holders of the office of Caliph, as recognized by most Muslims, the only period in which the Shia Imamate and the Caliphate were united to any degree. There was only one other exception: the Caliphate of Ali himself.

The Fatimids were famous for religious tolerance towards non-Ismaili sects of Islam as well as towards Jews, Maltese Christians and Coptic Christians, but there were some exceptions nevertheless.

Rise of the Fatimids 

The Fatimids came from Ifriqiya, modern-day Tunisia and eastern Algeria. The dynasty was founded in 909 by , who legitimised his claim through descent from Muhammad by way of his daughter Fātima as-Zahra and her husband , the first  Imām, hence the name al-Fātimiyyūn "Fatimid".

Abdullāh al-Mahdi's control soon extended over all of central Maghreb, an area consisting of the modern countries of Morocco, Algeria, Tunisia and Libya, which he ruled from Mahdia, his newly-built capital in Tunisia.

Decay and fall 
In the 1040s, the Zirids (governors of North Africa under the Fatimids) declared their independence from the Fatimids and their conversion to Sunni Islam, which led to the devastating Banū Hilal invasions.  After about 1070, the Fatimid hold on the Levant coast and parts of Syria was challenged first by Turkic (Seljuk) invasions, then the Crusades, so that Fatimid territory shrank until it consisted only of Egypt.

After the decay of the Fatimid political system in the 1160s, the Zengid ruler Nūr ad-Dīn had his general, Shirkuh, seize Egypt from the vizier Shawar in 1169.  Shirkuh died two months after taking power, and the rule went to his nephew, Saladin.  This began the Kurdish Ayyubid Dynasty.

Fatimid caliphs 
  (909-934) founder Fatimid dynasty
  (934-946)
  (946-953)
  (953-975) Egypt is conquered during his reign
  (975-996)
  (996-1021)
  (1021-1036)
  (1036-1094)
  (1094-1101) Quarrels over his succession led to the Nizari split.
  (1101-1130) The Fatimid rulers of Egypt after him are not recognized as Imams by Mustaali Taiyabi Ismailis.
  (1130-1149)
  (1149-1154)
  (1154-1160)
  (1160-1171).

Notes

Other websites 
 Fatimids entry in the Encyclopaedia of the Orient. 
 Institute of Ismaili Studies London. 

Arab people
Caliphates
Former countries in the Middle East
Former monarchies
Former monarchies of Africa
Former monarchies of Asia
Royal dynasties
909 establishments
12th-century disestablishments in Africa
12th-century disestablishments in Asia
10th-century establishments in Africa
10th-century establishments in Asia
1171 disestablishments
Maghreb

The Maghreb ( ) is the western part of the Arab world. It is in North Africa. The term is generally applied to all of Mauritania, Western Sahara, Morocco, Algeria, Tunisia, and Libya, but in older Arabic usage meant only the area of the three countries between the high ranges of the Atlas Mountains and the Mediterranean Sea (Morocco, Algeria and Tunisia). Historically, some writers also included Muslim ruled regions in Spain, Portugal, Sicily and Malta in the definition. Malta, in particular, still speaks a language based on its own Maghrebi Arabic variety: Maltese.

References

Other websites 

 Politics, economics, and human affairs analysis in the Maghhreb 
 Radio Online of the Maghreb 
 News and Views of the Maghreb

Regions of Africa
Plaintext

In cryptography, plaintext is the information which the sender want to transmit to the receiver(s).  

Before computers, plaintext meant text in the language of the communicating parties.  Since computers, the definition has been expanded. It now includes not only the electronic representation of text, such as emails and word processor documents, but also the computer representation of speech, music, pictures, videos, ATM and credit card transactions, sensor data, and so forth. That is basically any information which the communicating parties might wish to hide from others.  The plaintext is the normal representation of the data before any action has been taken to hide it.

The plaintext is used as input to an encryption algorithm; the output is termed ciphertext.  Some systems, however, use a cascade of layers of encryption (called 'rounds') in which case the ciphertext output of one encryption algorithm becomes the plaintext input to the next. Triple DES is an example.

Related pages
 Cleartext

Cryptography
Ciphertext

In cryptography, ciphertext (or cyphertext) refers to the output of the encryption process. Plaintext is turned into ciphertext using an algorithm (cipher). This makes it unreadable to anyone except those who own unique information about it, usually referred to as a key. 

Decryption is the reverse process of encryption. It takes the unreadable ciphertext as an input and makes it readable again in the form of plaintext.

Cryptography
Azad Kashmir Day

Azad Kashmir Day celebrates the 67th day of the Azad Jammu Kashmir government, created on 24 October 1947. However, most people celebrate it on 26 October as they class it as a lucky day once all the papers were signed and settled.

Kashmir
Holidays
Nyon

Nyon is a municipality in the district of Nyon in the canton of Vaud in Switzerland. It is found 25 kilometers north of Geneva, and is part of the Geneva metropolitan area. The town has (as of 2006) 17,267 people.

History 
Nyon was built by the Romans between 50 BCE and 44 BCE, and was called "Colonia Iulia Equestris" or "Colonia Equestris Noiodunum". It grew to be one of the most important Roman colonies in modern-day Switzerland, with a forum, a basilica and an amphitheater that was discovered in 1996.

Modern Day Nyon 
Today, Nyon has a high school (Gymnase de Nyon), a hospital, a movie theatre, hotels, restaurants, cafes and a popular tourist attraction - the castle. 
In the last week of July each year, Nyon hosts the Paléo Festival - a huge music festival.

Other websites 

Official website of the town (available in French, English and German)
Web site of the Roman Museum of Nyon (same languages as above link)
Paléo Festival
Rugby Club Nyon
Ultimate Frisbee Club, Les Mange-Disques de Nyon
La Redoute, Popular neighbourhood of Nyon

Municipalities of Vaud
Cities in Switzerland
Letterkenny

Letterkenny () is a town in County Donegal of the Ireland. It is  on the River Swilly and has a population of 17,586.

In 1824, when the first description of Letterkenny as a modern town was written, it was stated that: "Within half a mile is the Port of Ballyraine, whither vessels of 100 tons bring iron, salt and colonial produce and whence they export hides and butter". Nothing is left of the port now except the warehouses.

Letterkenny achieved town status in the early 1920s following the partition of Ireland.

References

Towns in Ireland
County Donegal
Thalwil

Thalwil is a municipality in the district of Horgen in the canton of Zürich in Switzerland.

History
Early Middle Ages Thalwil was Alemannic farmland.

Thalwil was originally four Wachten, or hamlets:
 Ludretikon, the oldest hamlet (mentioned in 915), bordering Rüschlikon
 Oberdorf (Upper Village), the area around the church
 Unterdorf (Lower Village), the area roughly south of the railway station
 Langnau am Albis, (which separated from Thalwil around 1713)

In the Middle Ages, most income was made in farming, vineyards and a small amount of fishing on the lake. 
Thalwil also has the oldest wood corporation in the Canton of Zurich, the Bannegg-Waldung. It was first mentioned in 1483.

Modern day Thalwil
Today, the economy of Thalwil is mostly some small and medium-sized businesses, and a wide range of shops. Most of the shops are located around Gotthardstrasse- the town centre.

The main source of Thalwil's wealth lies with its 7,000 commuters. These people live in Thalwil, but work in Zurich city. Today, Thalwil has left most of its farming past behind in exchange for a town of commuters, with its public transportation links, low tax and good quality of life.

Other websites 

Official website of the Thalwil Gemeinde 

Blog about life in Thalwil 
Thalwiler Anzeiger newspaper 

Cities in Switzerland
Municipalities of Zürich
Hearth

A hearth (har-th) is a brick or stone lined fireplace or oven that is used for cooking and heating. Historically, the hearth was the center of the home, as it provided heat for the house. Its Latin name is focus. That is why "focus" is used for many kinds of central point.

In more modern times, the hearth may be section of the fireplace that can be seen. This often includes tiles around the base of the fireplace and the floor.

References

Home
Jack-o'-lantern

A Jack-o'-lantern is a carved pumpkin, turnip, beet, or potato. In the 19th and 20th centuries people in Scotland and Ireland carved Halloween lanterns from large yellow turnips. This custom has become less prevalent in recent years as supermarkets have begun selling the larger and easier-to-carve American pumpkins. 

In Irish lore, the Jack-o'-lantern is from the story of Stingy Jack. Jack was a clever man who cheated the devil several times. Once when Jack was leaving hell, the devil threw him a glowing coal to light his way. Jack put the coal in a hollowed-out turnip to make the first "Jack-o'-lantern". Lore says Jack can still be seen wandering the world with his turnip lantern, especially around All Saints Day, November 1.

In the United States, the carved pumpkin was first associated with the harvest season in general, long before it became an emblem of Halloween. In 1900, an article on Thanksgiving entertaining recommended a lit Jack-o'-lantern as part of the festivities.

To make a Jack-o'-lantern, the top of the pumpkin surrounding the stump of the vine is cut off. This top will be used as a "lid" when the Jack-o'-lantern is completed. The seeds and pulp inside the pumpkin are scooped out using a spoon or one's hands. The seeds may be roasted in a hot oven, and then salted to make a snack.

Once the inside of the pumpkin is clean, a face is carved into one side of the pumpkin. The eyes and nose are usually triangles. The mouth is usually filled with jagged teeth. A candle, devotional candle in a candle-holder, or a flashlight is put inside the Jack-o'-lantern and lit. The "lid" is replaced. The lid may be placed slightly askew to keep the candle alit. 

In the United States, a completely carved and lit Jack-o'-lantern is put on the porch, the porch steps, or in a window to welcome trick-or-treaters on Halloween. Once the pumpkin is carved, it is good for nothing else and lasts only a day or two before it starts to rot. Pumpkins used to make Jack-o'-lanterns are inedible. In the United States, mischief-makers steal the Jack-o'-lanterns of their neighbors. The pumpkins are smashed in the street, dropped from a bridge, or otherwise destroyed.

References

  

Cucurbitaceae
West Coast blues

The West Coast blues is a type of blues music related to jazz and jump blues, with lots of piano sounds and jazz guitar solos, which originated from Texas blues musicians that moved to California in the 1940s.  West Coast blues also uses smooth, honey-toned vocals, often sounding similar to urban blues.

Texas and the West Coast

The best known West Coast blues musicians may be guitarist T-Bone Walker, famous for the song "Call It Stormy Monday (But Tuesday Is Just As Bad)", originally from Texas, he had made his first recordings in the late 1920s. During the early 1940's Walker moved to Los Angeles, where he recorded a lot of music for Capital, Black & White, and Imperial. Walker an electric guitar sound to the blues, prossibly doing more to make the use of electric guitar popular in blues than anyone else. Much of his material had a jazzy jump blues feel, which is typical of popular blues from California in the 1940s and 1950s. Other Texas bluesmen followed: Pianist/songwriter Amos Milburn, singer Percy Mayfield, famous for the song "Hit the Road Jack", and Charles Brown moved to Los Angeles. Guitarist Pee Wee Crayton divided his time between Los Angeles and San Francisco, while Lowell Fulson, from Texas by way of Oklahoma, moved to Oakland.
 
After the efforts of Tom Mazzolini, producer of the San Francisco Blues Festival, started in 1974, and the efforts of recording companies like Arhoolie and HighTone, the West Coast is one of the most important blues areas in the country.

Artist/Musicians

Footnotes

Other websites
Bay Area Blues Society 

Blues music
Bushfire

A bushfire is a wildfire that happens mostly in the Australian bush. Bush is the word for scrub, woodland or grassland of Australia and New Zealand. In south east and south west of Australia, bushfires are most common in the summer and early autumn. In the north of Australia, bushfires usually happen during winter which is the dry season. Many Australian plants burn easily. Eucalyptus trees have a high oil content which makes them burn. Over the last 40 years, Australian bushfires have cost around 2.5 billion Australian dollars. In the same period, Australian bushfires caused the death of around 250 people and the destruction of 4,554 homes.But these figures do not include the 173 people who died and the 2000 homes destroyed in the 2009 Victorian bushfires. They can also kill wildlife including rare koalas.

Related pages 
Wildfire
Fire ecology

References

Fire
Ecology
Artificial selection

Artificial selection is the intentional breeding of plants or animals. It means the same thing as selective breeding and is an ancient method of genetic engineering. 

Selective breeding is a technique used when breeding domesticated animals, such as dogs, pigeons or cattle. Some of these animals may have traits that a breeder will want to carry over to the next generation. The breeder will therefore select those animals to breed which have that quality, rather than those that do not.

Inbreeding is a particular kind of selective breeding, designed to produce a population which is genetically virtually identical.  Such populations are rarely viable outside the laboratory.  They lose fertility.  To control this, most breeds are outcrossed or backcrossed to wild-type individuals, or at least less inbred stock. The details differ from breed to breed.  The improvement when outcrossing is done is called hybrid vigour.

Charles Darwin used the example of artificial selection to introduce his idea of natural selection. Artificial selection may be contrasted with the process of natural selection. In natural selection, the differential reproduction of organisms with certain traits happens. This is because some variations help the organism to have better survival and reproduction. The process maintains or enhances the fitness of a population in its natural habitat. 

Artificial selection may sometimes be unintentional; it is thought that domestication of crops by early humans was largely unintentional.

References 

Classical genetics
Domesticated animals
Agriculture
Selectable marker

A selectable marker is a reporter gene introduced into a cell along with a gene insert. What this means is, the experimenter can tell the right gene is in the cell because the marker can be seen or detected.

Most often, this is used for  bacteria or for cells in culture. Selectable markers show the success of a transfection or other procedure meant to introduce foreign DNA into a cell. It is a technique in gene targeting and gene knockout.

Selectable markers are often antibiotic resistance genes; bacteria that have been subjected to a procedure to introduce foreign DNA are grown on a medium containing an antibiotic.  The antibiotic knocks out cells which do not have the resistant marker. Those bacterial colonies that can grow have successfully taken up and expressed the introduced genetic material.

An alternative to a selectable marker is a screenable marker, which allows the researcher to distinguish between wanted and unwanted cells.

Examples of selectable markers include:
Beta-lactamase which confers ampicillin resistance to bacterial hosts.
Neo gene from Tn5, which confers antibiotic resistance to kanamycin in bacteria and to geneticin in eukaryote cells.
Mutant FabI gene (mFabI) from E. coli genome, which confers triclosan resistance to the host.

References 

Genetic engineering
Evolutionary algorithm

In Computer Science, especially in artificial intelligence, evolutionary algorithms are a kind of algorithm that simulate evolution to optimise something. Each generation of solution is subjected to some kind of fitness function; those that survive are then recombined in some way to make the next generation of solution. This is done until a certain level of fitness is reached, or a determined number of generations have been used.

Artificial intelligence
Artificial life

Artificial life (commonly Alife or alife) is a field of study which examines systems related to life, its processes, and its evolution. This is done with simulations using computer models, robotics, and biochemistry. There are three main kinds of alife, named for their approaches:  soft, from software; hard, from hardware; and wet, from biochemistry. Artificial life imitates traditional biology by trying to recreate biological phenomena.  The term "artificial life" is often used to specifically refer to soft alife.

References

Scientific modeling
Nils Aall Barricelli

Nils Aall Barricelli (24 January 1912 – 27 January 1993) was a Norwegian-Italian mathematician.

Barricelli's early computer-assisted experiments in symbiogenesis and evolution are considered pioneering in artificial life research. Barricelli, who was independently rich, held an unpaid residency at the Institute for Advanced Study in Princeton, New Jersey in 1953, 1954. and 1956. He later worked at the University of California, Los Angeles, at Vanderbilt University (until 1964), in the Department of Genetics of the University of Washington, Seattle (until 1968) and then at the Mathematics Institute of the University of Oslo. Barricelli published in a variety of fields including virus genetics, DNA, theoretical biology, space flight, theoretical physics and mathematical language.

References

Other websites
 Barricelli's Universe (make-digital.com) 
 George Dyson TED talk discusses Barricelli

1912 births
1993 deaths
Norwegian mathematicians
Italian mathematicians
Ingo Rechenberg

Ingo Rechenberg''' (born January 20 1934 in Berlin) is a German computer scientist and professor. Rechenberg is a pioneer of the fields of evolutionary computation and artificial evolution.   In the 1960s and 1970s he invented a highly influential set of optimization methods known as evolution strategies (from German Evolutionsstrategie''). His group successfully applied the new algorithms to challenging problems such as aerodynamic wing design. These were the first serious technical applications of artificial evolution, an important subset of the still growing field of bionics.

Rechenberg was educated at the Technical University of Berlin and at the University of Cambridge. Since 1972 he has been a full professor at the  Technical University of Berlin, where he is heading the Department of Bionics and Evolution Techniques.

His awards include the Lifetime Achievement Award of the Evolutionary Programming Society (US, 1995) and the Evolutionary Computation Pioneer Award of the IEEE Neural Networks Society (US, 2002). In 1954, Rechenberg also became world champion in the field of model airplanes.

Selected bibliography 

 Ingo Rechenberg (1971): Evolutionsstrategie - Optimierung technischer Systeme nach Prinzipien der biologischen Evolution (PhD thesis). Reprinted by Fromman-Holzboog (1973).
 Ingo Rechenberg: Evolutionsstrategie '94. Stuttgart: Frommann-Holzboog 1994.

References

Other websites 

Rechenberg's Bionic's Lab in Berlin  (in German) and in English 

1934 births
Living people
Evolution strategy

Evolution strategies are ways to solve a problem using evolutionary algorithms. The term was coined by Ingo Rechenberg.

Artificial intelligence
John Henry Holland

John Henry Holland (February 2, 1929 – August 9, 2015) was an American scientist. He was Professor of Psychology and Professor of Electrical Engineering and Computer Science at the University of Michigan, Ann Arbor. He was a pioneer in complex system and nonlinear science. He was known as the father of genetic algorithms.

Holland died on August 9, 2015 in Ann Arbor, Michigan, aged 86.

References

1929 births
2015 deaths
American psychologists
Scientists from Indiana
Ontario Lacus

Ontario Lacus is a lake filled with methane and ethane near the south pole of Saturn's moon Titan.  It was identified as a hydrocarbon lake and confirmed by data from the Cassini spacecraft. This discovery was announced in the 31 July 2008 edition of Nature. Ontario Lacus is about 20,000 km2 in area, and is named after Lake Ontario in North America, which is a similar size and shape.

References

Other websites

Saturn's moons
Lakes
Penetrometer

A penetrometer is a device to test the strength of a material.

It is often used on soil. The penetrometer is dropped on soil or it is pressed against soil to measure how deep a hole it makes. This is a way to decide if soil is strong enough to build a road on. Scientists can use a penetrometer to measure how much moisture is in soil. Penetrometers are used on space probes such as the Cassini-Huygens probe, to measure the amount of moisture in soil on other planets.

Sources 
University of Arizona document, "An impact penetrometer for a landing spacecraft". 
A picture of a penetrometer from the European Space Agency (ESA) 

Geology
Measuring tools
Crème brûlée

Crème brûlée (or Crème brulée) is a dessert. It is made of custard. It is topped with a thin, brittle crust of caramelized sugar. It may be served cold, warm, or at room temperature. The custard is baked, and then sprinkled with sugar Casa  that is caramelized under a broiler or with a kitchen blowtorch. The custard is flavored with vanilla. Other flavorings include chocolate, orange liqueur, fruit, or other. The caramelized sugar crust can be covered with a liqueur and set on fire.

The exact origin of crème brûlée is uncertain. France, England, and Spain all claim to be the country where crème brûlée had its origin. The first printed recipe for a dessert called crème brûlée is from the 1691 edition of the French cookbook Le Cuisinier Royal et Bourgeois by Francois Massialot, a cook at the Palace of Versailles. That version was a sweet custard of egg yolks and milk with a burnt sugar crust. It is similar to the modern versions. In the second edition of the book, the dessert is called crème anglaise.  

At Trinity College, Cambridge the dessert was known as 'burnt cream'. The college crest was burnt into sugar on top of a custard using a hot iron. It may predate Massialot's cookbook with one authority claiming it was first served at Trinity in 1630.

Catalans claim their dessert known as crema catalana is the original. It is a rich custard often flavoured with cinnamon and lemon or orange zest topped with carmelized sugar. The Catalan version was first recorded in the 18th century. It is also called Crema de Sant Josep, after Saint Joseph, the husband of the Virgin Mary. In Spain and in many other parts of Europe, Saint Joseph’s Day is celebrated on 19 March. Crema Catalana is a traditional dessert served on this day.

References

Other websites 

A guide to crème brûlée history and how to prepare a recipe 

Desserts
Kraken Mare

Kraken Mare is the largest known lake on the surface of Saturn's moon Titan. It was discovered in 2007 by the Cassini probe and was named in 2008 after the Kraken, a legendary sea monster.

Kraken Mare is believed to be the largest of seas and lakes near Titan's north pole. It was discovered as a sea of hydrocarbons by radar pictures. Only a small part of the sea has been pictured by radar, but its full size is seen in visible light pictures. Kraken Mare is believed to be similar in size to the Caspian Sea.

An island in the sea is named Mayda Insula.

References

Other websites 

 Map of Titan's north pole, based on radar imagery, showing Kraken Mare's location

Saturn's moons
Ligeia Mare

Ligeia Mare is a lake on Titan at 79.0° N, 248.0° W, measuring around 500 km in width. It is named after Ligeia, one of the sirens in Greek mythology. Ligeia Mare has been a proposed lake to land the Titan Lake In-situ Sampling Propelled Explorer space probe

Other websites
Map of the liquid bodies in the north polar region of Titan

Saturn's moons
Keystream

In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message (the ciphertext).

The "characters" in the keystream can be bits, bytes, numbers or actual characters like A-Z depending on the usage case.

Usually each character in the keystream is either added, subtracted or XORed with a character in the plaintext to produce the ciphertext, using modular arithmetic.

Keystreams are used in the one-time pad cipher and in most stream ciphers. Block ciphers can also be used to produce keystreams. For example, the CTR mode (also known as Integer Counter Mode (ICM)) is a block mode that makes a block cipher produce a keystream then turns the block cipher into a stream cipher.

Example 

In this simple example we will use only the English alphabet of 26 characters from a-z, therefore we will not encrypt numbers, commas, spaces and other symbols. As we have only 26 characters the random numbers in the keystream have to be at least between 0 and 25.

To encrypt we add the keystream numbers to the plaintext. And to decrypt we subtract the same keystream numbers from the ciphertext to get the plaintext.

If a ciphertext number becomes larger than 25 we wrap it to a value between 0-25. I.e. 26 becomes 0 and 27 becomes 1 and so on. (Such wrapping is called modular arithmetic.)

Here the plaintext message "attack at dawn" is combined by addition with the keystream "kjcngmlhylyu" and produces the ciphertext "kcvniwlabluh".

References 

 Handbook of Applied Cryptography by Menezes, van Oorschot and Vanstone (2001), chapter 1, 6 and 7. 

Cryptography
Noor Jehan

Noor Jehan () was the adopted stage name for Allah Wasai (September 21, 1926 – December 23, 2000). She was a Pakistani singer and actress. She is renowned as one of the greatest singers of her time in the Indian subcontinent and was given the honorific title of Mallika-e-Tarranum (, English: the queen of melody). She achieved special national recognition and popularity in Pakistan with her patriotic songs of 1965, which elevated her to an iconic level. 

Along with Ahmed Rushdi, she holds the record for having given voice to the largest number of film songs in the history of Pakistani cinema. She is also considered to be the first female Pakistani film director.

Noor Jehan was awarded the Pakistan President's Award in 1965.

She married Shaukat Hussain Rizvi in 1942. The marriage ended in 1953 with divorce. The couple had three children, including their singer daughter Zil-e-Huma. She then married Ejaz Durrani in 1959. The second marriage also produced three children. It ended in divorce in 1970.

In 2000, Jehan was hospitalized in Karachi and suffered a heart attack. Jehan died as a result of heart failure.

References

Other websites
 

1926 births
2000 deaths
Pakistani movie actors
Pakistani singers
Punjabi people
Nusrat Fateh Ali Khan

Nusrat Fateh Ali Khan (, October 13, 1948 – August 16, 1997), was a Pakistani musician. He was a singer of qawwali, the devotional music of the Sufis (a mystical tradition in Islam). In 2006, Time magazine included him in their list of "Asian Heroes'.

Traditionally, qawwali is a performing art which is passed down with in the family. Nusrat's family has been performing qawwali for the last 600 years. Among other honorary titles given to him, Nusrat was called Shahenshah-e-Qawwali, meaning The Emperor of Qawwali.

Other websites 
 

1948 births
1997 deaths
Pakistani people
Punjabi people
Pakistani singers
Bollywood playback singers
Aziz Mian

Aziz Mian Qawwal () (April 17, 1942 – December 6, 2000) was a Pakistani singer, most famous for his performing of Qawwalis. Aziz Mian was born as Abdul Aziz () in Delhi, British India. The exclamation Mian, which he often used in his qawwalis, became part of his stage name. He began to introduce himself as Aziz Mian Mairthi. The word Mairthi refers to Meerut, a city in northern India, from which he migrated to Pakistan in 1947.

At the age of ten, he began learning the art of Qawwali under the tutelage of Ustad Abdul Wahid Khan. He received sixteen years of training at the Data Ganj Baksh School of Lahore, and obtained a degree in Urdu literature from the University of Punjab, Lahore.

1942 births
2000 deaths
Pakistani singers
People from Delhi
Kashmir Solidarity Day

Kashmir Solidarity Day has been celebrated on 5 February each year since 1990. It is a day of protest against Indian control of part of Kashmir. It is a national holiday in Pakistan.

References

Kashmir
Holidays
National emblem of Bangladesh

The National Emblem of Bangladesh was adopted shortly after independence in 1971. 

Located on the emblem is a White water lily, that is bordered on two sides by rice sheaves. Above the water lilly are four stars and a three-leaf clover of jute leaves. The water lily is the country's national flower, and is representative of the many rivers that run through Bangladesh. Rice represents its presence as the staple food of Bangladesh, and for the agriculture of that nation. The four stars represent the four founding principles that were originally enshrined in the first constitution of Bangladesh in 1972: Nationalism, Secularism, Socialism, and Democracy. 

The details of the emblem is given as quoted below:
The national emblem of the Republic is the national flower Shapla (Nymphaea pubescens) resting on water, having on each side an ear of paddy and being surmounted by three connected leaves of jute with two stars on each side of the leaves. - Constitution of Bangladesh Article 4(3) 

The Government of Bangladesh has adopted Education, Nationalism and Democracy as its "National Motto".

References

Bangladesh
Bangladesh
Instrument of Surrender

The Instrument of Surrender () was a written agreement that enabled the surrender of the Pakistan Armed Forces in the Bangladesh Liberation War. The surrender took place at the Ramna Race Course in Dacca on December 16, 1971. Lieutenant-General A A K Niazi, joint commander of the Pakistan Armed Forces in East Pakistan,  and Lieutenant General Jagjit Singh Aurora, joint commander of the Bangladesh-India Allied Forces, signed the instrument amid thousands of cheering crowds at the race course. Air Commodore A. K. Khandker, Deputy Commander-in-Chief of the Bangladesh Armed Forces, and Lieutenant General J F R Jacob of the Indian Eastern Command, acted as witnesses to the surrender.

Subsequently, around 93,000 Pakistani troops and officials were taken as prisoners-of-war by the Indian Army, the largest number of POWs since World War II. They were later repatriated in 1973 under the terms of the Delhi Agreement.

Text of the Instrument

The Pakistan Eastern Command agree to surrender all Pakistan Armed Forces in Bangladesh to Lieutenant-General Jagjit Singh Aurora, General Officer Commanding in Chief of the Indian and Bangladesh forces in the Eastern Theatre. This surrender includes all Pakistan land, air and naval forces as also all para-military forces and civil armed forces. These forces will lay down their arms and surrender at the places where they are currently located to the nearest regular troops under the command of Lieutenant- General Jagjit Singh Aurora. 

The Pakistan Eastern Command shall come under the orders of Lieutenant-General Jagjit Singh Aurora as soon as this instrument has been signed. Disobedience of orders will be regarded as a breach of the surrender terms and will be dealt with in accordance with the accepted laws and usages of war. The decision of Lieutenant-General Jagjit Singh Aurora will be final, should any doubt arise as to the meaning or interpretation of the surrender terms. 

Lieutenant- General Jagjit Singh Aurora gives a solemn assurance that personnel who surrender will be treated with dignity and respect that soldiers are entitled to in accordance with the provisions of the Geneva Convention and guarantees the safety and well-being of all PAKISTAN military and para-military forces who surrender. Protection will be provided to foreign nationals, ethnic minorities and personnel of Western Pakistan origin by the forces under the command of Lieutenant - General Jagjit Singh Aurora. 

Signed: 

(Jagjit Singh Aurora) Lieutenant-General General Officer Commanding in Chief Indian and Bangladesh Forces in the Eastern Theatre 

(Amir Abdullah Khan Niazi) Lieutenant-General Martial Law Administrator Zone B and Commander Eastern Command (Pakistan) 

16 December 1971" 

This document can be seen on display in the National Museum in Delhi (as of January 2012)

References

1971 in Bangladesh
1971 in Pakistan
Bangladesh Liberation War
Product cipher

In cryptography, a product cipher is a popular type of stream ciphers that works by executing in sequence a number of simple transformations such as substitution, permutation, and modular arithmetic. 

Product ciphers usually consist of iterations of several rounds of the same algorithm. Individual rounds themselves are not secure. However, it is hoped that a sufficiently long chain of rounds loads the cipher with sufficient confusion and diffusion properties to make it resistant to cryptanalysis. 

A product cipher that uses only substitutions and permutations is called a SP-network. Feistel ciphers are another important class of product ciphers.

Cryptography
Islamic Republic

Islamic Republic is the name given to forms of government of several states. These states have Islam as a state religion and are governed by the principles of the Islamic law called Sharia. Some of these countries have both Sharia and civil law. Laws made by the state cannot contradict Sharia in some of these countries, and in other countries civil law is more dominant than Sharia law. 

The following states call themselves Islamic Republic (non-exhaustive list)
Iran (after Shah Mohammad Reza Pahlavi was overthrown in 1979)
Pakistan (Since the constitution of 1956, state founded to provide a homeland for Muslims living in Colonial India, in 1947)
Afghanistan (since the overthrow of the Taliban in 2001)
Mauritania (since 1958)
Sudan
Comoros (Federal Islamic Republic)
The Gambia (since December 2015)

Despite the similar name the countries differ greatly in their governments and laws. Of the Islamic republics, only Iran is a theocracy.

Politics of Pakistan
Mauritania
Iran
Politics of Afghanistan
Forms of government
Key schedule

In cryptography,  the so-called product ciphers are a certain kind of ciphers, where the decryption of data is done in "rounds". The general setup of each round is the same, except for some hard-coded parameters and a part of the cipher key, called a subkey. A key schedule is an algorithm that, given the key, calculates the subkeys for these rounds.

Some types of key schedules 

Some ciphers have simple key schedules. For example, the block cipher TEA simply splits the 128-bit key into four 32-bit pieces and uses them repeatedly in successive rounds.

DES uses a key schedule where the 56 bit key is divided into two 28-bit halves then each half is treated separately. In successive rounds, both halves are rotated left by one or two bits (specified for each round), and then 48 subkey bits are selected by Permuted Choice 2 (PC-2) — 24 bits from the left half, and 24 from the right. The rotations mean that a different set of bits is used in each subkey; each bit is used in approximately 14 out of the 16 subkeys.

In an effort to avoid simple relationships between the cipher key and the subkeys, to resist such forms of cryptanalysis as related-key attacks and slide attacks, many modern ciphers use much more complex key schedules, such as algorithms that use a one-way function to generate an "expanded key" from which subkeys are drawn. Some ciphers, such as Rijndael (AES) and Blowfish, use parts of the cipher algorithm itself for this key expansion, sometimes initialized with some "nothing up my sleeve numbers". Other ciphers, such as RC5, expand keys with functions that are somewhat or completely different from the encryption functions.

Notes 

Knudsen and Mathiassen (2004) give some experimental evidence that indicate that the key schedule plays a part in providing strength against linear and differential cryptanalysis. For toy Feistel ciphers, it was observed that those with complex and well-designed key schedules can reach a uniform distribution for the probabilities of differentials and linear hulls faster than those with poorly-designed key schedules.

References
 Lars R. Knudsen and John Erik Mathiassen, On the Role of Key Schedules in Attacks on Iterated Ciphers, ESORICS 2004, pp322–334.

Cryptography
EFF DES cracker

In cryptography, the EFF DES cracker (nicknamed "Deep Crack") is a machine built by the Electronic Frontier Foundation (EFF) to perform a brute force search of DES cipher's key space — that is, to decrypt an encrypted message by trying every possible key. The aim in doing this was to prove that DES's key is not long enough to be secure.

The DES uses a 56-bit key, meaning that there are 256 possible keys under which a message can be encrypted. This is approximately 7.21 (more than 72 quadrillion). When DES was approved as a federal standard in 1976, a machine fast enough to test such a number of keys in a reasonable time would have cost an unreasonable amount of money to build.

Other websites
 The DES Cracker page on EFF's site 
 Photos of the machine on Cryptography Research's site
 COPACOBANA, an off-the-shelf DES cracking device

Cryptography
Security clearance

A security clearance is a status granted (approved) to individuals allowing them access to classified information, e.g. state secrets. It is something like permission or a license. The term "security clearance" is also sometimes used in private organizations that have a formal process of selecting employees to access "sensitive information". 

A clearance by itself is normally not sufficient to gain access; the organization must determine that the cleared person "needs to know" the information. No one is supposed to be granted access to classified information only because of rank, position, or a security clearance.

National security
Sensitive information

Sensitive information is information or knowledge that might result in loss of an advantage or level of security if exposed to others who might be unfriends or have low or unknown trustability.

Loss, misuse, modification or unauthorized access to sensitive information can negatively affect the privacy of an individual, trade secrets of a business or even the security, internal and foreign affairs of a nation depending on the level of sensitivity and nature of the information. 

The term classified information generally refers to information that is subject to special security classification regulations imposed by many national governments. The term "Unclassified" as used in the below refers to information that is not subject to security classification regulations. Information can be reclassified to a different level or declassified (made available to the public) depending on changes of situation or new intelligence.

National security
Trade secret

A trade secret is a formula, practice, process, design, instrument, pattern, or a collection of information which is not generally known, invented or created, by which a business can obtain an economic advantage over competitors or customers. In some jurisdictions, such secrets are referred to as "confidential information" or "classified information".

With its broad definition of eligible subject matter, trade secret law protects a wide range of valuable information, including information that would not be eligible for protection under existing patent, trademark, or copyright law. This could include formulae and recipes, proprietary databases, business processes and methods, information about costs, pricing, margins, overhead, manufacturing processes, proprietary computer software programs, customer lists, and strategic plans and marketing programs.

There are three factors that are common to all definitions of a trade secret, a trade secret is information that:
 Is not generally known to the public;
 Grants some sort of economic benefit on its holder (where this benefit must derive specifically from its not being generally known, not just from the value of the information itself);
 Is the subject of reasonable efforts to maintain its secrecy.
The unauthorized acquisition, use, or disclosure of such secret information in a manner contrary to honest commercial practices by others is regarded as an unfair practice and a violation of the trade secret protection.

References

Secrecy
Trade
Intellectual property law
Rock Steady

Rock Steady is the fifth studio album by the American alternative rock band No Doubt. It was released on December 11, 2001. The album was influenced a lot by reggae, dancehall, and electronica, compared to their previous albums. A lot of music critics saw this and gave the album good reviews. For example, Rolling Stone magazine put the album as the 316th greatest album of all time in their book Rolling Stone's List of the 500 Greatest Albums of All Time. It was nominated for Best Pop Vocal Album at the 2003 Grammy Awards. Four singles were released from the album. The first single, "Hey Baby", won the Grammy Award for Best Pop Performance by a Duo or Group with Vocal. The second single was nominated for Best Dance Recording. The third single, "Underneath It All", was released August 15 2002. It won a Grammy Award for Best Pop Performance by a Duo or Group with Vocal at the 2004 Grammy Awards. The album's last single, "Running", was released July 1 2003.

List of songs
"Intro"
"Hella Good"
"Hey Baby" (featuring Bounty Killer)
"Making Out"
"Underneath It All" (featuring Lady Saw)
"Detective"
"Don't Let Me Down"
"Start the Fire"
"Running"
"In My Head"
"Platinum Blonde Life"
"Waiting Room" (featuring Prince)
"Rock Steady"

The iTunes version of the album has two extra songs.
"Underneath It All" (live)
"Just a Girl" (live)

References

2001 albums
No Doubt albums
Meet-in-the-middle attack

The Meet-in-the-middle attack is a cryptographic attack which, like the birthday attack, makes use of a space-time tradeoff. While the birthday attack attempts to find two values in the domain of a function that map to the same value in its range, the meet-in-the-middle attack attempts to find a value in each of the ranges and domains of the composition of two functions such that the forward mapping of one through the first function is the same as the inverse image of the other through the second function—quite literally meeting in the middle of the composed function.

It was first developed as an attack on an attempted expansion of a block cipher by Diffie and Hellman in 1977. When trying to improve the security of a block cipher, one might get the idea to simply use two independent keys to encrypt the data twice and think that this would square the security of the double-encryption scheme. Certainly, an exhaustive search of all possible combination of keys would take  attempts if each key is n bits long, compared to the  attempts required for a single key. However, Diffie and Hellman, discovered a time-memory tradeoff that could break the scheme in only double the time to break the single-encryption scheme. The attack works by encrypting from one end and decrypting from the other end, thus meeting in the middle.

Assume the attacker knows a set of plaintext and ciphertext: P and C. That is,
 ,
where E is the encryption function (cipher), and K1 and K2 are the two keys.

The attacker can then compute EK(P) for all possible keys K and store the results in memory. Afterwards he can decrypt the ciphertext by computing DK(C) for each K. Any matches between these two resulting sets are likely to reveal the correct keys. (To speed up the comparison, the EK(P) set is stored in an in-memory lookup table, then each DK(C) can be matched against the values in the lookup table to find the candidate keys.)

Once the matches are discovered, they can be verified with a second test-set of plaintext and ciphertext. If the keysize is n, this attack uses only  encryptions (and  space) in contrast to the naive attack, which needs  encryptions (but only  space).

Related pages
Birthday attack

References

Cryptography