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Topic: Autokey cipher

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Vigenere cipher

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Monoalphabetic substitution cipher

Substitution cipher

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Transposition cipher

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	Autokey cipher - Biocrawler (Site not responding. Last check: 2007-10-13)
		An autokey cipher is a cipher which incorporates the message (the plaintext) into the key.
		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.
		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.
	www.biocrawler.com /encyclopedia/Autokey_cipher (524 words)

	Autokey cipher
		An autokey cipher, or self-synchronizing stream cipher, is a cipher which incorporates the message into the key.
		This text-autokey cipher was hailed as "le chiffre indéchiffrable", and was indeed undecipherable for over 200 years, until Charles Babbage discovered the means of breaking the cipher.
		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.
	www.ebroadcast.com.au /lookup/encyclopedia/au/Autokey_cipher.html (412 words)

	Self-Authenticating cryptographic apparatus - Patent 6912284
		Autokey encipherment or encryption refers generally to a substitution cipher in which the key, following the application of an initial key, is determined in whole or in part by preceeding elements of the key or cipher.
		An important advantage of an autokey system is its ability to self-synchronize; i.e., the receiving key generator is not required to be preset to a previously determined value prior to receiving and decoding cipher messages.
		Cipher text autokey systems continuously self-synchronize throughout the transmission, while key autokey systems may be initially synchronized by temporarily operating in a CTAK mode until synchronization is achieved.
	www.freepatentsonline.com /6912284.html (2396 words)

	Braingle: Vigenere Cipher
		In a Caesar Cipher, each letter of the alphabet is shifted along some number of places; for example, in a Caesar cipher of shift 3, A would become D, B would become E and so on.
		A Gronsfeld cipher is identical to the Vigenere cipher with the exception that only 10 rows are used which allows the keyword to be a number instead of a word.
		An Autokey cipher is identical to the Vigenère cipher with the exception that instead of creating a keyword by repeating one word over and over, the keyword is constructed by appending the keyword to the begining of the actual plaintext message.
	www.braingle.com /brainteasers/codes/vigenere.php (467 words)

	Autokey code generator - Patent 4343967
		Some of the outputs of the matrix means are connected together to furnish the autokey code, and the remainder of the outputs are connected to the control means to furnish control signals therefor.
		A matrix suitable for use in the autokey generator of the present invention is described in a paper entitled, "Rectifier Networks for Multi-Position Switching" by D. Brown and N. Rochester, appearing at pages 139-147 of the Proceedings of the I.R.E. for February 1949 or in the above-identified application.
		1 develops an autokey code at terminal 39 which is a function solely of the preceding four binary digits of the pulse train applied to input terminal 10 and of the setting of wheel 37.
	www.freepatentsonline.com /4343967.html (4050 words)

	Cryptology and Cryptography
		The simplest substitution cipher is one where the alphabet of the cipher is merely a shift of the plaintext alphabet, for example, A might be encrypted as B, C as D and so forth.
		For many years this cipher was thought to be impregnable and it is rumoured that a well known scientific magazine pronounced it "uncrackable" as late as 1917, despite the fact that it had been broken by then.
		However, even though running-key ciphers eliminate periodicity it is still possible to cryptanalyse them by means of several methods, however the job of the cryptanalyst is made much harder and a cryptanalyst would require a much larger segment of ciphertext to solve a running-key cipher than one with a repeating key.
	mehr.sharif.edu /~farhat/cryptography-cryptology.htm (9095 words)

	4 Many Caesars: the Vigenère Cipher
		Despite the fact that the method of breaking the Vigenére cipher had been published 50 years earlier, the cipher was widely held to be unbreakable until the 1920s, being described as ``impossible of translation'' in an article appearing in Scientific American in 1917.
		The Vigenère cipher is named after Blaise de Vigenère, a sixteenth century diplomat and cryptographer, although the cipher was invented by Giovan Batista Belaso in 1553.
		This is a type of autokey cipher, because the key is (semi-)automatically generated by the message itself.
	www.math.sunysb.edu /~scott/papers/MSTP/crypto/4Many_Caesars.html (676 words)

	95082301.HTM
		In contrast, in a good block cipher, every input bit is diffused throughout the block, even to "earlier" bits.
		This means that a block cipher can take advantage of any and all of the uniqueness in a plaintext block.
		Ciphers which depend on algorithmic operations -- even nonlinear operations -- seem more likely to be vulnerable to attack than ciphers which contain massive internal state.
	www.ciphersbyritter.com /NEWS/95082301.HTM (688 words)

	Ritter's Crypto Glossary and Dictionary of Technical Cryptography (Site not responding. Last check: 2007-10-13)
		A block cipher operates on a block of data (for example, multiple bytes) in a single ciphering, as opposed to a stream cipher, which operates on bytes or bits as they occur.
		It is also possible for a stream cipher to be re-keyed or re-originate frequently, and so appear to operate on "blocks." Such a cipher, however, would not have the overall diffusion we normally associate with a block cipher, and so might usefully be regarded as a stream meta-cipher with a stream cipher component.
		When a codebook attack is possible on a block cipher, the complexity of the attack is controlled by the size of the block (that is, the number of elements in the codebook) and not the strength of the cipher.
	packetstormsecurity.nl /crypt/GLOSSARY.HTM (13874 words)

	Classic Cryptography:Vigenère
		Blaise de Vigenère actually produced a more sophisticated autokey cipher, but through an accident of history his name has become attached to this weaker cipher.
		The cipher also requires a key, the cipher text is formed by first writing the key underneath the plain text.
		Then we break up the cipher text into groups of 9, in which we can assume that all of the first letters in each group were encrypted with the same letter, all the second letters were encrypted with the same letter, and so on.
	library.thinkquest.org /27158/concept1_5.html (522 words)

	Autokey cipher - Wikipedia, the free encyclopedia
		A tabula recta for use with an autokey cipher
		An autokey cipher (also known as the autoclave cipher
		) is a cipher which incorporates the message (the plaintext) into the key.
	en.wikipedia.org /wiki/Autokey_cipher (744 words)

	Polyalphabetic Substitution
		The idea of using substitution ciphers that change during the course of a message was a very important step forwards in cryptography.
		The plaintext alphabet on his cipher disk was in order, and included the digits 1 through 4 for forming codewords from a small vocabulary.
		Cipher disks are harder to make than slides, but they do look prettier.
	www.quadibloc.com /crypto/pp010303.htm (6453 words)

	ONE-TIME PAD CRYPTOGRAPHY
		For very long messages, the autokey can be applied to one block of the K stream at a time as it is retrieved from secondary storage, provided that message keys are not restricted to block boundaries.
		Each pair of correspondents could have a unique autokey used to produce their L key stream, then they would apply a second autokey to produce the key stream for a specific time period.
		Starting with a limited supply of a true-random key, a simple autokey cipher is used to generate additional random key material indefinitely.
	www.mastersoftware.biz /crypt005.htm (2197 words)

	Next years Cipher Challenge \| Harry's Page \| Home of the National Cipher Challenge (Site not responding. Last check: 2007-10-13)
		We have 16 ciphers (counting A and B as seperate) now, and although there were 16 'messages' listed in 2002 only 14 were encrypted.
		I see no reason why ciphers this year should be any more difficult than ciphers last year- in an ideal world we would want the challenge to be an ongoing thing, year after year, and for this to work it will need to continue to be accessible to new codebreakers as well as old hands.
		If you are putting a cipher in a comment, could you observe the same conditions as Harry mentioned for posts, or your comment probably won't be published.
	www.cipher.maths.soton.ac.uk /node/34 (2499 words)

	Stream Ciphers Using Variable Amounts of RNG State
		Another factor affecting "use in practice" is that many ciphers are available free, which thus limits the reward for the research and development needed to produce and have confidence in new and different ciphering approaches.
		By not establishing a for-pay industry of cipher development, society is forced to rely upon ciphers produced and analyzed "for free," typically by academics (who are, of course, paid).
		That is: 1) a conventional stream cipher, composed of RNG and additive combiner; 2) the RNG producing confusion in variable-size units; 3) XOR combining of confusion and data; and 4) autokey (ciphertext feedback) operation.
	www.ciphersbyritter.com /NEWS6/KEYSTRM.HTM (8315 words)

	Pigpen cipher - Wikipedia, the free encyclopedia
		The pigpen cipher uses graphical symbols assigned according to a key similar to the above diagram.
		The pigpen cipher (sometimes called the masonic cipher or Freemason's cipher) is a simple substitution cipher exchanging letters for symbols based on a grid.
		The Elian Script is a variation of this cipher, used as art.
	en.wikipedia.org /wiki/Pigpen_cipher (156 words)

	A QUICK OVERVIEW OF CRYPTOGRAPHY
		Stream ciphers Most cryptographic methods, from ancient to modern, fall into a few broad classes: Secret method Inherent key Hidden key Secret key Public key Private key In secret method cryptography the strength of the cipher comes from keeping the method itself secret.
		The most common example is the simple substitution cipher, often found on newspaper puzzle pages, where each letter of the alphabet is consistently replaced by a different letter of the alphabet.
		The simplest form of substitution cipher uses a table in which all of the blocks of a given size appear in scrambled order.
	www.mastersoftware.biz /crypt-ov.htm (2484 words)

	[No title] (Site not responding. Last check: 2007-10-13)
		Later, in the 19th century, the invention of Belaso's cipher was misattributed to Vigenère.
		This reputation was not deserved since Kasiski entirely broke the cipher in the 19th century and some skilled cryptanalysts could occasionally break the cipher in the 16th century.
		The Vigenère cipher is simple enough to be a field cipher if it is used in conjunction with cipher disks.
	www.people.vcu.edu /~james/c691/VigenereNotes.doc (507 words)

	Amazon.com: "Autokey Cipher": Key Phrase page (Site not responding. Last check: 2007-10-13)
		Antokey ciphers and cipher feedback systems are examples of additive self- synchronous stream ciphers [103].
		An autokey cipher is one in which the key is derived from the message it enciphers.
		History of Cryptography (Continued) 1564 Bellaso published an autokey cipher improving on the work of Cardano, who appears to have invented the idea.' 1623 Sir Francis Bacon described a cipher...
	www.amazon.com /phrase/Autokey-Cipher (552 words)

	Short History of Crypto
		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.
	www.jproc.ca /crypto/crypto_hist.html (3458 words)

	[No title]
		In this project you are to write a program which attacks and solves an autokey cipher.
		One of the factors taken into consideration in evaluating your program will be how well it performs on a particular autokey cipher.
		The idea is to modify their Vigenere ciphering systems by putting them in a CBC mode.
	www.cs.umbc.edu /~stephens/crypto/PROJECTS/project1sp2006f.html (1081 words)

	CSC290 Crypto Exercises (Site not responding. Last check: 2007-10-13)
		A further write-up, presumably in PDF, giving your main results, perhaps for this case ciphers you broke, passwords you found, etc. Here are some guidelines for the format and my expectations for these reports.
		Others might be a few paragraphs (how you broke a simple substituation cipher and what capabilities you think might be useful in general) to a few pages.
		Second is an Original Cipher used for an encrypted part of a document in the prof's past.
	www.cs.rochester.edu /u/brown/Crypto/assts/projects/old_exercises.html (1521 words)

	Atbash - Free net encyclopedia
		Atbash is a simple substitution cipher for the Hebrew alphabet.
		It consists of substituting aleph (the first letter) for tav (the last), beth (the second) for shin (one before last), and so on, reversing the alphabet.
		It is a very weak cipher because it only has one possible key, and it is a simple monoalphabetic substitution cipher.
	www.netipedia.com /index.php/Atbash (204 words)

	Braingle: Autokey Cipher
		To encrypt a plaintext message using the Vigenère Cipher, one locates the row with the first letter to be encrypted, and the column with the first letter of the keyword.
		The ciphertext letter is located at the intersection of the row and column.
		Enciphering and deciphering the message is performed using the exact same method as the Vigenère Cipher.
	www.braingle.com /brainteasers/codes/autokey.php (139 words)

	Completion of Programs - nano
		Where each letter of plaintext is mapped to a unique letter in the ciphertext.
		Progresses through each of the 26 Cæsar cipher keys or until the user selects one as being the correct cipher
		Provided with a keyword of length n, the algorithm uses n different Cæsar ciphers for each of the letter positions 1...
	www.nanonanonano.net /projects/cryptography/report3part2 (1158 words)

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