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Topic: Vigenere cipher

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	Substitution cipher - Wikipedia, the free encyclopedia
		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.
		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.
		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.
	en.wikipedia.org /wiki/Substitution_cipher (2600 words)

	Autokey cipher - Wikipedia, the free encyclopedia
		The first autokey cipher was invented by Girolamo Cardano, and, although it contained a weakness that made it easy to break, a number of attempts were made by other cryptographers to produce an autokey system that was not trivial to break; eventually one was invented by Blaise de Vigenère.
		Most modern stream ciphers are based on pseudorandom number generators: the key is used to initialize the generator, and either key bytes or plaintext bytes are fed back into the generator to produce more bytes.
		Some stream ciphers are said to be "self-synchronizing", because the next key byte usually depends only on the previous N bytes of the message.
	en.wikipedia.org /wiki/Autokey_cipher (737 words)

	Cryptography -- Vigenere Cipher
		The Vigenere Cipher, proposed by Blaise de Vigenere from the court of Henry III of France in the sixteenth century, is a polyalphabetic substitution based on the following tableau:
		A variation of it, known as the Gronsfeld cipher, did catch on in Germany and was widely used in Central Europe.
		Given the structure of the Vigenere tableau, this is equivalent to using 9 distinct simple substitution ciphers, each of which was derived from 1 of the 26 possible Caesar shifts given in the tableau.
	www.trincoll.edu /depts/cpsc/cryptography/vigenere.html (1337 words)

	vigenere.nb
		The Vigenere cipher is probably the most commonly known example of a polyalphabetic cipher, attributed (incorrectly) to Blaise de Vigenere in the 16th century.
		The Vigenere cipher is interesting not because it has been broken, but because its solution involved, or at least stimulated, the first systematic application of statistical methods to cryptanalysis.
		The Vigenere cipher is a special case of a periodic polyalphabetic cipher, and works as follows.
	mywebpages.comcast.net /erfarmer201/vigenere (1035 words)

	Vigenere Cipher: Description (Site not responding. Last check: 2007-10-31)
		Vigenere ciphers are simple poly-alphabetic ciphers derived from Caesar ciphers.
		A character at position p in the plaintext is encrypted using the (p mod n) + 1th cipher in the tuple.
		Vigenere ciphers form a group where the keylength of the product of two vigenere ciphers is the lcm of the keylengths of the factor keys.
	www.muth.org /Robert/Cipher/vigenere/description.html (161 words)

	How the Vigenere Cipher Works : A detailed explanation into an important cryptographic historical discovery (Site not responding. Last check: 2007-10-31)
		It is a type of substitution cipher in which each letter in plaintext is replaced by a letter some fixed number of positions further down the alphabet.
		The Vigenere cipher is a method of encryption which uses several different Caesar ciphers based on the letters of a keyword and is considered a simple form of polyalphabetic substitution.
		For example, a shift of 4 would have an A become E, a B be F, etc. The Vigenere Cipher furthers this idea by using several Caesar ciphers of varying shift values.
	www.xramp.com /resources/vigenerecipherdetails (784 words)

	Clay Mathematics Institute
		In the mid nineteenth century the Vigenère cipher was broken.
		The Caesar cipher was reputedly used by the Emperor Julius Caesar to communicate with his generals.
		The Vigenère cipher was invented in the mid sixteenth century by Blaise de Vigenère, who worked in the court of King Henry III of France.
	www.claymath.org /posters/primes/vigenere.php (575 words)

	IM-QPP: REF IRON MOUTH ARTICLE
		In Figure 7 are listed the repeated letter combinations in the ciphered message, together with the distances they are from each other. The next step is to take the distances and break them down into their factors. Doing so, we obtain the values in Figure 8.
		To test the period you've chosen, you need to segment the cipher into six portions. For the test period six, this has been done in Figure 9. The next step is to do a frequency count for each of the six message segments, which we've done in Figure 10.
		I have tested the Kasiski method out on this month's Vigenere cipher and it should, relatively easily, enable you to guess the correct period for the cipher. From there, you're on your own, although as I have said, the most difficult part of cryptanalysis of periodic ciphers is the determination of the keyword's period.
	members.tripod.com /~ironmouth/mp-ref-ima.html (362 words)

	CORE 139 S04: Lab 2
		(A trivial cipher is one in which the ciphertext is the same as the plaintext; a non-useful cipher is one in which several different plaintext letters are enciphered to the same ciphertext letter.) Explain.
		S is the cipher alphabet used for the substitution cipher plus the value of k.
		This cipher is not especially strong, though it is better than the individual techniques (especially if you do not know the encryption algorithm); see Körner's "Passage 2" for another combination of rotation and substitution which is stronger than "Passage 1".
	cs.colgate.edu /faculty/nevison/FSemWeb/hw/lab1-sol.html (1774 words)

	Illuminations: Code Crackers
		The use of the keyword makes the Vigenere cipher more difficult to decode, because the length of the keyword is unknown and the number of possibilities has dramatically increased.
		The process of decoding a message, whether using the Caesar cipher, the Vigenere cipher, or some other method, involves undoing the encoding process, which is equivalent to using the inverse process.
		The Vigenere cipher was used by the Confederates during the Civil War, and the Enigma cipher was used by the Germans in World War II.
	illuminations.nctm.org /LessonDetail.aspx?ID=L618 (1307 words)

	Vigenere Ciphers
		So a shift cipher is a special case of a Vigenere cipher in which the key length is 1.
		The Vigenere cipher used to be state of the art.
		A Vigenere key is used for one message and the key is longer than the plain text.
	www-rohan.sdsu.edu /~gawron/crypto/lectures/vigenere.html (1402 words)

	8 The Hill Cipher
		The Hill cipher works by viewing a group of letters as a vector, and encryption is done by matrix multiplication.
		The real strength of the Hill cipher is that it can be adapted to work on large blocks of text without having to use huge numbers as we did in the previous section.
		If the length of the key for the Vigenère cipher is the same as the length of the letter-blocks, this yields an affine cipher AX+B, where A is an n x n matrix, X is our vector of n plaintext letters, and B is the n-vector corresponding to the Vigenère key.
	www.math.sunysb.edu /~scott/papers/MSTP/crypto/8Hill_Cipher.html (604 words)

	VIGENERE CIPHER WITH THE TI-83, THE Mathematics and Computer Education - Find Articles
		Encryption and decryption using the Vigenere Cipher was originally described in terms of a table known as the Vigenere Square and a secret keyword.
		The Vigenere Cipher is named after the Frenchman Blaise de Vigenere and uses a table known as the Vigenere Square.
		To encrypt this message using the Vigenere Cipher, Michael replaces each plaintext letter with the letter that lies in the Vigenere Square at the intersection of the column headed by the plaintext letter and the row headed by the corresponding keyword letter.
	www.findarticles.com /p/articles/mi_qa3950/is_200401/ai_n9372568 (871 words)

	CRYPTOCOM Classified - Vigenère Cipher - Overview
		The Vigenère cipher is a method of encryption that uses a series of different Caesar ciphers based on the letters of a keyword.
		The invention of the Vigenère cipher was misattributed to Blaise de Vigenère in the 19th century; it was originally described by a Giovan Batista Belaso in his 1553 book La cifra del. Sig.
		This cipher is well-known because while it is easy to understand and implement, it often appears to beginners to be unbreakable.
	www.csci.csusb.edu /public/crypto/game/VigenereCipher_Overview.php (409 words)

	Why is Vigenère so Strong ?
		If we encrypt the same piece of text using the monoalphabetic substitution cipher and the Vigenère Cipher, we can see why the latter cipher is so much stronger than the former.
		For many years, cryptography was nothing more than a tool that helped him his diplomatic work, but at the age of thirty nine, Vigènere decided that he had amassed enough money to be able to abandon his career and concentrate on a life of study.
		The high frequencies have merely moved to different letters (e.g., the highest peak has moved from E to D, because E has been encrypted as D), and they can be used to crack the cipher.
	www.simonsingh.net /The_Black_Chamber/vigenere_strong.html (288 words)

	Chapter Ciphers in JavaScript
		A cipher is an algorithm or set of algorithms that systematically convert a sender's intended message text to what appears to be meaningless text, which can be converted back to the sender's original message only by authorized recipients.
		Ciphers in which both the sender and the recipient use the same key to encrypt and decrypt the message are said to be part of a
		Ciphers in which data is encrypted and decrypted with a pair of keys--one freely distributed to the public, the other known only to the recipient--are said to be part of a
	www.oreilly.com /catalog/jscook/chapter/ch09.html (4694 words)

	Vigenere Cipher (Site not responding. Last check: 2007-10-31)
		A transposition cipher is an encoding process that does not change any of the letters of the original message, but changes the position of the letters.
		Given a sufficiently large encoded message derived using a monoalphabetic substitution cipher, it can readily be "cracked" by comparing the frequency of letter occurrences in the coded message with the frequency of letter occurrences in the language used for the message.
		The Vigenere cipher is a polyalphabetic cipher based on using successively shifted alphabets, a different shifted alphabet for each of the 26 English letters.
	astro.temple.edu /~dhill001/vigenere/vigenere.html (1653 words)

	Vigenere Cryptanalysis (Site not responding. Last check: 2007-10-31)
		A poly-alphabetic cipher is a substitution cipher which allows single letters of plaintext to be replaced with multiple letters of ciphertext.
		A prevalent poly-alphabetic cipher is the Vigenere, cipher where a matrix is set up of all possible shift ciphers, ones starting with 'A' to ones starting with 'Z'.
		We assumed a Vigenere cipher was used for encryption and attempts were then made to find the key.
	www.cs.virginia.edu /~cmt5n/Classwork/Crypt/Shaun/vigenerecrypt.html (400 words)

	Cryptography Tutorial - Polyalphabetic Ciphers: The Vigenere Cipher (Site not responding. Last check: 2007-10-31)
		The Vigenere Cipher is an improvement of the Caesar Cipher but not as secure as the unbreakable One Time Pad.
		The vulnerability of the cipher is due to the periodicity of the keyword.
		Cipher letters in same groups stem from plain letters that were shifted by the same same number of positions, they are Caesar shifts.
	www.antilles.k12.vi.us /math/cryptotut/vigenere.htm (1347 words)

	Vigenere encryption (Site not responding. Last check: 2007-10-31)
		The Vigenere encryption was the creation of the French diplomat, Blaise de Vigenere, 1523-1596.
		Rather he viewed the cypher as a substitution cipher where a different alphabet was used for the next letter of the message, with the alphabets repeating periodically --- according to some key.
		He proposed a method for breaking a Vigenere cipher that consisted of finding the length of the keyword and then dividing the message into that many simple substitution cryptograms.
	www.math.tamu.edu /~dallen/hollywood/breaking/v.htm (339 words)

	Vigenère Cipher
		The Vigenère Cipher is one of the truly great breakthroughs in the development of cryptography.
		This section explains how the cipher works and why it is so strong compared to all other ciphers that preceded it.
		Born in 1404, Alberti was one the leading figures of the Renaissance; a painter, composer, poet and philosopher.
	www.simonsingh.net /The_Black_Chamber/vigenere_cipher.html (340 words)

	Vigenere Cipher in Lisp
		The Vigenere cipher is an old cryptosystem from the days of pen and paper.
		Vigenere is not sufficient for security in a modern, computerized environment.
		The Vigenere cipher itself is probably of interest and use only to people who care about the history of cryptology.
	cybertiggyr.com /gene/vig (1534 words)

	Paj's Home: Cryptography: Vigenere Cipher (Site not responding. Last check: 2007-10-31)
		This cipher was invented in the 16th century, and first written down by a French diplomat, Blaise de Vigenère.
		For Vigenere ciphertexts, the coincidence index is higher for shifts that are a multiple of the key length than otherwise (can you see why?).
		The program calculates the first 256 shifts, and finds the shortest length for which all shifts that are a multiple of this length have a coincidence index greater than 6%, which it suggests as the key length.
	pajhome.org.uk /crypt/vigenere.html (864 words)

	JBO - Vigenère Cipher (Site not responding. Last check: 2007-10-31)
		The Key button permits settting of an alphabetic keyword which is used to determine which of the available cipher alphabets is used for each letter of the plaintext.
		Our implementation of this cipher allows you to choose a keyword or phrase up to the length of the data being encrypted, and includes the traditional twenty-six alphabets, i.e.
		There is no file size limit in Vigenère Cipher although your operating system and memory configuration may impose such limits.
	www.jbosoftware.co.uk /vigenere.htm (290 words)

	Sharky's Vigenere Cipher (Site not responding. Last check: 2007-10-31)
		Vigenere coding is one of the most ancient forms of cryptography.
		In a Vigenere cipher, messages are encoded by mapping letters to numeric values and adding the plaintext values to the keytext values, modulo the number of letters in the alphabet.
		Vigenere ciphers with moderate keys are appropriate for situations that do not require failproof security.
	sharkysoft.com /misc/vigenere (363 words)

	KiXtart.org - official site: KiXgolf: Vigenere Cipher - Private coding
		You are to write a UDF that encrypts and decrypts alphanumeric text based on a modified Vigenere Cipher using a cipher table consisting of a group of uppercase alpha letters, lowercase alpha letters, and numbers.
		The modifed Vigenere cipher will add an offset to the encrypted characters on a per-word basis corresponding to the wordnumber in the sentence.
		In the standard Vigenere cipher, you're using the ciphers that are shifted by one character when you go down the cipher tableu.
	www.kixtart.org /ubbthreads/showflat.php?Cat=&Number=122604 (2403 words)

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