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Topic: Polyalphabetic cipher

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Substitution cipher

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	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		Even Alberti's implementation of his polyalphabetic cipher was rather easy to break (the capitalized letter is a major clue to the cryptanalyst).
		Polyalphabetic substitution cipher designers seem to have concentrated on obscuring the choice of a few such alphabets (repeating as needed), not on the increased security possible by using many and never repeating any.
		It was not until the mid-1800s (in Babbage's secret work during the Crimean War) and Friedrich Kasiski's generally equivalent public disclosure some years later, that cryptanalysis of well-implemented polyalphabetic ciphers got anywhere at all.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=polyalphabetic_cipher (653 words)

	HIGH-SECURITY CIPHER
		Polyalphabetic ciphers are inherently fast, in most cases require little storage, and are easy to implement in hardware or software.
		The process is simple: you start with a basic cipher, then you examine all of the known ways that such ciphers have been broken in the past, and you devise ways to defeat those attacks.
		The basis for cracking such a polyalphabetic cipher is to discover several sections of text that have been enciphered with the same part of the key stream.
	www.mastersoftware.biz /crypt003.htm (3667 words)

	Polyalphabetic Crypto Program
		The Polyalphabetic Cipher (often referred to as a Vigenère
		Normally, the cipher alphabet is 26 letters arranged alphabetically (a-z).
		It also allows a 'codemaker' to create a polyalphabetic cipher system of his own design and has a crib dragging function for cracking polyalphabetic ciphertext.
	www.secretcodebreaker.com /polyprog.html (163 words)

	The Alberti Cipher
		A polyalphabetic cipher is similar to a Substitution, cipher.
		The Alberti Cipher and all its relations, the polyalphabetic ciphers, are distinguished by their effect on letter frequencies.
		Polyalphabetic ciphers such as the one developed by Alberti represent the backbone of modern encryption, and gave rise to such marvels as the enigma machine, and have come a long way from the Renaissance Man's "unbreakable cipher."
	starbase.trincoll.edu /~crypto/historical/alberti.html (1700 words)

	User Manual (Site not responding. Last check: )
		Substitution ciphers are characterized by a substitution of a character in the original plain text message by the corresponding character in the cipher alphabet, often according to some protocol derived from a predetermined key.
		A polyalphabetic substitution cipher is fairly similar to a monoalphabetic one, the difference being that instead of using a single cipher alphabet, multiple cipher alphabets are used.
		These types of ciphers are fairly straightforward to break by considering a block of text as characters in a matrix and performing row or column shifts and swaps until a recognizable message is derived.
	www.lgfl.net /xerxes/web/user_manual.htm (4128 words)

	Polyalphabetic cipher at AllExperts
		The VigenÃ¨re cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case.
		Even Alberti's implementation of his polyalphabetic cipher was rather easy to break (the capitalized letter is a major clue to the cryptanalyst).
		Polyalphabetic substitution cipher designers seem to have concentrated on obscuring the choice of a few such alphabets (repeating as needed), not on the increased security possible by using many and never repeating any.
	en.allexperts.com /e/p/po/polyalphabetic_cipher.htm (557 words)

	Polyalphabetic cipher - CompWisdom (Site not responding. Last check: )
		Polyalphabetic ciphers are inherently fast, in most cases require little storage, and are easy to implement in hardware or software.
		The autokey cipher was generally called "the undecipherable cipher", though due to popular confusion many thought that the weaker polyalphabetic cipher was the "undecipherable" one.
		The polyalphabetic cipher was, at least in principle, for it was not properly used for several hundred years, the most signifcant advance in cryptography since before Julius Caesar's time.
	www.compwisdom.com /topics/Polyalphabetic-cipher (1932 words)

	Reference.com/Encyclopedia/Polyalphabetic cipher
		The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case.
		Alberti used a Caesar cipher to encrypt a message, but whenever he wanted to he would switch to a different alphabet, indicating that he had done so by capitalizing the first letter encrypted with the new alphabet.
		Polyalphabetic substitution cipher designers seem to have concentrated on obscuring the choice of a few such alphabets (repeating as needed), not on the increased security possible by using many and never repeating any.
	www.reference.com /browse/wiki/Polyalphabetic_cipher (692 words)

	Substitution cipher Information
		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.
		Polyalphabetic substitution ciphers were first described in 1467 by Leone Battista Alberti in the form of disks.
		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.
	www.bookrags.com /wiki/Substitution_cipher (2577 words)

	Background
		Substitution ciphers are characterized by a substitution of a character in the original plain text messageby the corresponding character in the cipher alphabet, often according to some protocol derived from a predetermined key.
		A polyalphabetic substitution cipher is fairly similar to a monalphabetic one, the difference being that instead of using a single cipher alphabet, multiple cipher alphabets are used.The simplest type of polyalphabetic cipher, the Vigenere cipher, can use as many as twenty-six distinct cipher alphabets, each a simple rotation of the normally ordered alphabet.
		These types of ciphers are fairly straightforward to break by considering a block of text as characters in a matrix and performing row or columnshifts and swaps until a recognizable message is derived.
	www.cs.unc.edu /~stotts/COMP145/homes/crypt/userManual/user_back.html (1392 words)

	Polyalphabetic Substitution
		The plaintext alphabet on his cipher disk was in order, and included the digits 1 through 4 for forming codewords from a small vocabulary.
		Incidentally, for the polyalphabetic encryption of a stream of message digits by a stream of key digits, it is not strictly necessary to use only addition without carries.
		Since it is only required that the operation table for polyalphabetic combining of a keystream with text be a Latin square for it to function in an ideal fashion, it is not necessary that the table be patterned after that for a group; but groups certainly are a common source of tables.
	www.quadibloc.com /crypto/pp010303.htm (6453 words)

	Cipher Glossary
		The cipher alphabet can also consist of numbers or any other characters, but in all cases it dictates the replacements for letters in the original message.
		polyalphabetic substitution cipher : A substitution cipher in which the cipher alphabet changes during the encryption, for example the Vigenère cipher.
		The Vigenère square contains 26 separate cipher alphabets, each one a Caesar-shifted alphabet, and a keyword defines which cipher alphabet should be used to encrypt each letter of a message.
	www.fortunecity.com /emachines/e11/86/cipherglos.html (1226 words)

	Cryptography
		Ciphers act on each character of a message, transforming it according to some repeatable rule or algorithm.
		The main weakness of the monoalphabetic ciphers is that their frequency distribution reflects the distribution of the underlying alphabet.
		Polyalphabetic cipher overcomes these problems to give an algorithm that is more foolproof.
	members.rediff.com /geeteshk/project1/3-Cryptography.htm (1402 words)

	History of Secrecy
		The monoalphabetic cipher simply substitutes each letter of the alphabet with a symbol, so that A might always be replaced with +, and B with 8, and so on.
		This cipher was secure for centuries, until codebreakers noticed that each letter has an average frequency and no matter how the letter is disguised the new symbol will take on the frequency of the letter it represents.
		Again, each cipher depended on choosing a key, known only by the sender and the receiver, which specified the exact rules of encryption for a particular message.
	www.simonsingh.com /History_of_the_Science_of_Secrecy.html (992 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)

	Cryptology \| Wheel Cipher: Introduction
		The wheel cipher, and in the process the polyalphabetic cipher, was created by the Leon Battista Alberti.
		The reason is because his polyalphabetic cipher, the first, used a mechanism.
		The principles already discussed in those lessons for polyalphabetic ciphers remain true for this lesson, and to spare repetition, let me say simply that you should read the polyalphabetic section if you haven't done so yet.
	library.thinkquest.org /27993/crypto/mech/wheel1.shtml (459 words)

	CME's Cryptography Timeline
		He invented a steganographic cipher in which each letter was represented as a word taken from a succession of columns.
		Colonel Decius Wadsworth produced a geared cipher disk with a different number of letters in the plain and cipher alphabets -- resulting in a progressive cipher in which alphabets are used irregularly, depending on the plaintext used.
		This cipher uses a keyed array of letters to make a digraphic cipher which is easy to use in the field.
	world.std.com /~cme/html/timeline.html (3709 words)

	Brief overview of classical cryptography - Quantiki (Site not responding. Last check: )
		Indeed, polyalphabetic ciphers invented by the main contributors to the field at the time, such as Johannes Trithemius (1462-1516), Blaise de Vigenere (1523-1596), and Giovanni Battista Della Porta (1535-1615), were considered unbreakable for at least another 200 years.
		The first description of a systematic method of breaking polyalphabetic ciphers was published in 1863 by the Prussian colonel Friedrich Wilhelm Kasiski (1805-1881), but, according to some sources (for example, Simon Singh, The code book), Charles Babbage (1791-1871) had worked out the same method in private sometime in the 1850s.
		The basic idea of breaking polyalphabetic ciphers is based on the observation that if we use N different substitutions in a periodic fashion then every Nth character in the cryptogram is enciphered with the same monoalphabetic cipher.
	www.quantiki.org /wiki/index.php/Brief_overview_of_classical_cryptography (1918 words)

	History of Secrecy
		The monoalphabetic cipher simply substitutes each letter of the alphabet with a symbol, so that A might always be replaced with +, and B with 8, and so on.
		This cipher was secure for centuries, until codebreakers noticed that each letter has an average frequency and no matter how the letter is disguised the new symbol will take on the frequency of the letter it represents.
		Again, each cipher depended on choosing a key, known only by the sender and the receiver, which specified the exact rules of encryption for a particular message.
	www.simonsingh.net /History_of_the_Science_of_Secrecy.html (992 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.
		Use the Polyalphabetic Alignment tool to determine which of ciphers #5-#9 are encrypted with the same key as #4 and what the offset is.
	cs.colgate.edu /faculty/nevison/FSemWeb/hw/lab1-sol.html (1774 words)

	The Den
		Polyalphabetic Cipher --------------------- Blaise de Vigenere made his own cipher system, but through a historical accident, he has also been linked to the following, weaker system.
		Although it would have to be much, much longer than for the ciphers listed in page 2.
		For example, take the plaintext "baby vox is the best" which then becomes: b b v x s h b s a y o i t e e t Take this and your new ciphertext will be "bbvxshbsayoiteet".
	www.angelfire.com /magic/nexusb0mb/info-cryptosingle3.htm (342 words)

	[No title]
		Polyalphabetic substitution is an hybrid between transposition and substitution.
		The cipher is obtained by replacing a letter in the message by the intersection of current message character and current key character in the table.
		Theoritically, an equiprobable cipher would not be a nice idea for a one-way hash function as it would be easily subject to collisions, but as I explained, the result seems to be equiprobable while there is a limited range of possible substitution for a fixed key.
	www.phrack.org /archives/62/p62-0x0e_A_Polyalphabetic_Substitution_Cipher.txt (4277 words)

	Cryptanalysis / Congruence of Length: P[len] = C[len]
		Assuming an equal length then there must exist a definite cipher character for each plaintext character or at least has to be connected to a definite plaintext character mediated by the concerning function.
		The length of cipher sequences no longer match with the respective plaintext length in all cases and the encrypted character often is shifted to another location than its position in the plaintext.
		In case of a block cipher for instance a block of ciphertext and the concerned plaintext block are given [#51].
	www.multi-matrix.de /EQLENGTH.HTM (3236 words)

	CSI660T Programming Graduate Project
		Since a polyalphabetic cipher uses multiple key substitutions, it cannot be cracked by looking at the letter distribution like a mono-alphabetic (simple) substitution cipher.
		Polyalphabetic ciphers do not show the same distribution of letter frequencies that makes a monoalphabetic substitution cipher so easy to crack.
		However, a common technique to defend polyalphabetic ciphers against this attack is to keep individual messages short and to shift the key between uses.
	www.cs.albany.edu /~berg/csi445/Assignments/project.html (1941 words)

	Cipher Glossary
		The cipher alphabet can also consist of numbers or any other characters, but in all cases it dictates the replacements for letters in the original message.
		polyalphabetic substitution cipher : A substitution cipher in which the cipher alphabet changes during the encryption, for example the Vigenère cipher.
		Vigenère cipher : A polyalphabetic cipher which was developed around 1500.
	members.fortunecity.com /templarser/cipherglos.html (1226 words)

	How the Vigenere Cipher Works : A detailed explanation into an important cryptographic historical discovery (Site not responding. Last check: )
		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 Caesar cipher is named after Julius Caesar, who used it with a three letter shift formula to protect messages during battle, according to Suetonius, a prominent Roman historian.
		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.
	www.xramp.com /resources/vigenerecipherdetails (812 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)

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