In cryptography, the Polybius square, also known as the Polybius checkerboard, is a device invented by the Ancient Greek historian and scholar Polybius, described in Hist. X.45.6 ff., for fractionating plaintext characters so that they can be represented by a smaller set of symbols. The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write) is the study of message secrecy. ... Note: This article contains special characters. ... A historian is an individual who studies history and who writes on history. ... Polybius (c. ... In classical cryptography, a transposition cipher changes one character from the plaintext to another (to decrypt the reverse is done). ... In cryptography, plaintext is information used as input to an encryption algorithm; the output is termed ciphertext. ...

Basic form

The original square used the Greek alphabet, but can be used with any alphabet. In fact, it has also been used with Japanese hiragana (see cryptography in Japan). With the modern English alphabet, in typical form, it appears thus: The Greek alphabet is an alphabet that has been used to write the Greek language since about the 9th century BCE. It was the first alphabet in the narrow sense, that is, a writing system using a separate symbol for each vowel and consonant alike. ... Japanese writing Kanji Kana Hiragana Katakana Hentaigana Manyōgana Uses Furigana Okurigana Rōmaji Hiragana ) is a Japanese syllabary, one component of the Japanese writing system, along with katakana and kanji; the Latin alphabet is also used in some cases. ... There is not much cryptological history in Japan - prior to the twentieth century, only a few simple codes were used and there seems to have been no practice of cryptanalysis at all. ... The modern English alphabet consists of the 26 letters[1] of the Latin alphabet: The exact shape of printed letters varies depending on the typeface. ...

Each letter is then represented by its co-ordinates in the grid. Thus "BAT" becomes "12 11 44", for example. Because 26 characters do not quite fit in a nice square, we round down to the next lowest square number by combining two letters - I and J, usually. (Polybius had no such problem because the Greek alphabet he was using had 24 letters). Alternatively, we could add digits as well and get a 6 × 6 grid. Such a larger grid might also be used for the Cyrillic alphabet, which has 33 letters. The Greek alphabet is an alphabet that has been used to write the Greek language since about the 9th century BCE. It was the first alphabet in the narrow sense, that is, a writing system using a separate symbol for each vowel and consonant alike. ... The Cyrillic alphabet (pronounced also called azbuka, from the old name of the first two letters) is actually a family of alphabets, subsets of which are used by a wide variety of Slavic languages—Belarusian, Bulgarian, Macedonian, Russian, Rusyn, Serbian, and Ukrainian—as well as many other languages of the...

Telegraphy and steganography

Polybius did not originally conceive of his device as a cipher so much as an aid to telegraphy; he suggested the symbols could be signalled by holding up pairs of sets of torches. It has also been used, in the form of the "knock code", to signal messages between cells in prisons by tapping the numbers on pipes or walls. In this form it is said to have been used by nihilist prisoners of the Russian Czars, and also by American prisoners of war in the Vietnam War. Indeed it can be signalled in many simple ways (flashing lamps, blasts of sound, drums, smoke signals) and is much easier to learn than more sophisticated codes like the Morse code. However, it is also somewhat less efficient than the more complex codes. Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraphy (from the Greek words tele (τηλε) = far and graphein (γραφειν) = write) is the long-distance transmission of written messages without physical transport of letters, originally by changing something that could be observed from a distance (optical telegraphy). ... A burning torch, discarded on the road in the wake of the Lewes Bonfire Night celebrations. ... The Tap Code is a code, commonly used by prisoners in jail to communicate with one another. ... This article is about the Russian cultural and political movement. ... Tsar, (Bulgarian цар�, Russian царь; often spelled Czar or Tzar in English), was the title used for the autocratic rulers of the First and Second Bulgarian Empires since 913, in Serbia in the middle of the 14th century, and in Russia from 1547 to 1917. ... Geneva Convention definition A prisoner of war (POW) is a soldier, sailor, airman, or marine who is imprisoned by an enemy power during or immediately after an armed conflict. ... Combatants Republic of Vietnam United States Republic of Korea Thailand Australia New Zealand The Philippines National Front for the Liberation of South Vietnam Democratic Republic of Vietnam People’s Republic of China Democratic Peoples Republic of Korea Strength US 1,000,000 South Korea 300,000 Australia 48,000... This article or section should be merged with Drum (communication) Jungle drums are an early form of long distance communication. ... A smoke signal is a form of visual communication used over a long distance, developed both in the Americas and in China. ... 1922 Chart of the Morse Code Letters and Numerals Morse code is a method for transmitting telegraphic information, using standardized sequences of short and long elements to represent the letters, numerals, punctuation and special characters of a message. ...

The simple representation also lends itself to steganography. The figures from one to five can be indicated by knots in a string, stitches on a quilt, letters squashed together before a wider space, or many other simple ways. Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message itself is not disguised, but the content is obscured. ... Some knots: 1. ...

Cryptography

By itself the Polybius square is not terribly secure, even if used with a mixed alphabet. The pairs of digits, taken together, just form a simple substitution in which the symbols happen to be pairs of digits. However a Polybius square offers the possibility of fractionation, leading toward Claude E. Shannon's confusion and diffusion. As such it is a useful component in several ciphers such as the ADFGVX cipher, the Nihilist cipher and the bifid 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. ... In classical cryptography, a transposition cipher changes one character from the plaintext to another (to decrypt the reverse is done). ... 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. ... 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. ... This article is about algorithms for encryption and decryption. ... In cryptography, the ADFGVX cipher was a field cipher used by the German Army during World War I. ADFGVX was in fact an extension of an earlier cipher called ADFGX. Invented by Colonel Fritz Nebel and introduced in March 1918, the cipher was a fractionating transposition cipher which combined a... -1... In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion. ...

External links

• Online Polybius Square encoder/decoder