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Topic: Index of coincidence

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	Cryptanalysis of the Vigenere cipher by the index of coincidence method
		) must be closer to the index of coincidence of the original text.
		The difference between two distributions is measured using the mutual index of coincidence.
		The more different the distributions are, the smaller the mutual index of coincidence.
	www.math.boun.edu.tr /instructors/karabudak/math462/asg/asg1/IndexOfCoincidence.htm (349 words)

	Coincidence theory - The Black Vault Encyclopedia Project (Site not responding. Last check: 2007-10-08)
		The term coincidence theory is used by proponents of controversial theories (often called conspiracy theorists) to counter those who dismiss their claims; they mean to express thus that these dismissals rely on too many coincidences to be plausible.
		They argue that a coincidence theory was disseminated by means of propaganda and media manipulation to advance the social or economic interest of a party and/or to hide another version of the facts that might damage that party's credibility or public image, as by establishing that party's guilt in an instance of crime or scandal.
		Coincidence theories, according to those who identify and denounce them, are calculated to exploit the gullibility and ignorance of those to whom they are communicated.
	www.blackvault.com /wiki/index.php/Coincidence_theory (338 words)

	Index of coincidence - Wikipedia, the free encyclopedia
		In cryptography, coincidence counting is the technique (invented by William F. Friedman) of putting two texts side-by-side and counting the number of times that a letter appears in the same position in both texts.
		This count, as a ratio of the total, is known as the index of coincidence.
		Various forms of Index of Coincidence have been devised; the "delta" I.C. (given by the formula above) in effect measures the autocorrelation of a single distribution, whereas a "kappa" I.C. is used when matching two text strings.
	en.wikipedia.org /wiki/Index_of_coincidence (935 words)

	Index of coincidence
		In cryptography, coincidence counting is the technique (invented by William F. Friedman) of putting two texts side-by-side and counting the number of times that a letter appears next to itself in both copies.
		Coincidence counting can help determine when two texts are written in the same language, using the same alphabet.
		For such texts, the coincidence count will be distinctly higher than the coincidence count for texts in different languages, or using different alphabets, or gibberish texts.
	publicliterature.org /en/wikipedia/i/in/index_of_coincidence.html (471 words)

	vigenere.nb
		In addition to finding the length of the keyword, a variant of the index of coincidence may also be used to determine the actual letters of the keyword.
		The mutual index of coincidence for two blocks of text is the probability that two randomly selected letters, one from each block, will be identical.
		By successively "shifting" the letters in one of the blocks (or equivalently, repeatedly encrypting with key 'b'), and noting the shift which results in the greatest mutual index of coincidence, the relationship between the two corresponding key letters may be determined.
	mywebpages.comcast.net /erfarmer201/vigenere/index.html (1035 words)

	CORE 139 S04: Lab 1
		The index of coincidence is useful because the probability of getting two identical letters depends on the distribution of letters in the bag.
		The index of coincidence I is the sum of [n
		Use the Index of Coincidence tool to find the index of coincidence for each column of ciphertext to verify that the correct length was found for the keyword.
	cs.colgate.edu /faculty/nevison/FSemWeb/hw/lab1.html (1985 words)

	A Coincidental Note (Site not responding. Last check: 2007-10-08)
		The index of coincidence of a sample is calculated by rotating the letters to the right and finding the probability of finding the same letter in the same location.
		For example, the index of coincidence of \texttt{ackgaknarf} with a shift of three is.3.
		Rotating the alphabet does not change the index of coincidence, so it can be used to identify the length of the key used in a Vignere cipher.
	www.cise.ufl.edu /~acm/HSPC/1997/questions/coincidence.txt (416 words)

	Coincidence - Wikipedia, the free encyclopedia
		Coincidence is the noteworthy alignment of two or more events or circumstances without obvious causal connection.
		A coincidence does not prove a relationship, but related events may be expected to have a higher index of coincidence.
		In optics, coincidence is also used to refer to two or more incident beams of light that strike the same point at the same time.
	en.wikipedia.org /wiki/Coincidence (229 words)

	10/20/97 SHINING A LIGHT ON 'CLOSET INDEX FUNDS'
		What you actually might own is a ''closet index fund.'' That's one with similar volatility and returns as the S&P--but with a sales charge, or ''load,'' as high as 6.5%, plus annual expenses of $1 or more for every $100 invested.
		By comparison, true index funds, which automatically invest in a list of stocks in proportions that reflect the makeup of the S&P, are almost always sold ''no-load,'' with expenses as low as 20 cents of every $100 invested.
		The fund is heavier in energy and financial stocks and lighter in utilities than the S&P. Spokespersons for MFS Massachusetts Investors Trust and State Street Research Investment also emphasized that their funds' sector-by-sector makeup is different from that of the S&P, and the high R2s are coincidental.
	www.businessweek.com /1997/42/b3549128.htm (1216 words)

	The Redundancy of English
		2000-10-30 JPeschel: "The index of coincidence is a statistical measure of the redundancy of text.
		The index of coincidence is a statistical measure of the redundancy of text.
		Around 1920, William Friedman published the article, "The Index of Coincidence and its Applications in Cryptography." http://www.aegeanparkpress.com/books_by_author.html The expected IC of English is around.667.
	www.ciphersbyritter.com /NEWS6/REDUN.HTM (1331 words)

	CORE 139 S04: Index of Coincidence Tool
		To verify that breaking the ciphertext down into a number of columns leads to monoalphabetic ciphers for each column, enter the number of columns in the "period" box and click "test period".
		The output shows the index of coincidence for each column graphically and numerically.
		Split the text into the number of columns specified by the value of "period" and compute the index of coincidence for each.
	cs.colgate.edu /faculty/nevison/FSemWeb/tools/coincidence.html (142 words)

	Chris Christensen's Summer 2001 MAT115
		The Friedman test results provide evidence of that: the index of coincidence is 0.0408 (which suggests that the cipher is polyalphabetic) and the estimated length of the keyword is 9.4855.
		The Friedman test results are: the index of coincidence is 0.0749 (which suggest that the cipher is monoalphabetic) and the estimated length of the keyword (which is useless information for this exercise) is 0.7327.
		The Friedman test results are: the index of coincidence is 0.0671 and the estimated length of the keyword is 0.9283.
	www.nku.edu /~christensen/ccsa.html (693 words)

	b>CHAPTER I RESULTS OF SOME COMPUTER ANALYSES OF THE VALIDITY OF THE BEALE CIPHERS
		William F. Friedman proposed the use of an index of coincidence K (for kappa) in which the probability of the coincidence of identical characters at certain positions in an enciphered message would be expressed as a percentage.
		For reasons which are apparent upon reflection, the values of the index of coincidence are symmetrical for positions equidistant left and right from identical central characters.
		The computer was also called upon to calculate the index of coincidence K1, K2 and K3 for Ciphers 1, 2 and 3 respectively.
	www.myoutbox.net /bch1.htm (2366 words)

	Helena Independent Record (Site not responding. Last check: 2007-10-08)
		In his Carroll talk, Winkel used a simple cipher to measure the "index of coincidence" in a cipher once sent to Edgar Allen Poe when he worked as a columnist at "Alexander's Weekly Messenger" in Philadelphia.
		Winkel said that the index of coincidence is based on the redundancy of text.
		From there, Winkel calculates the index of coincidence, determines any shifts within the alphabet, and finally, applies a mathematical formula to test the cipher piece by piece.
	www.helenair.com /articles/2004/03/22/top/a01032204_01.txt (660 words)

	calculating greatest common factor
		To determine the index of coincidence of a particular piece oftext,take the text, rotate it by some random number of places, and write therotated text underneath the original text.
		The index of coincidence is the number of places in which the sameletteroccurs in both strings of text.
		In the case where the rotation is a multiple of the cycle length, thelettersthat are lined up underneath each other are encoded using the sameshift,and the usual English index of coincidence would be expected, becausetheindex of coincidence is invariant under a single letter cipher.
	www.softmath.com /tutorials2/calculating-greatest-common-factor.html (2873 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		Qn2: Phase 1: Part I: This is because the index of coincidence comes from statistics.
		Consider a random key with length N. when finding the index for 1~N-1, because the same position are encrypted by randomly different key character, the index may like the one of random texts (around 3.8%).
		But when finding the index for N, because the same position is encrypted by the same key character, the encrypted text may act like a normal English text.
	acc6.its.brooklyn.cuny.edu /~qsun/cg/No1/ans.doc (523 words)

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