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| | HIGH-SECURITY CIPHER |
 | | Polyalphabetic ciphers are inherently fast, in most cases require little storage, and are easy to implement in hardware or software. | | | Is the cipher for hand use, for computer use, or to be implemented in some specific type of hardware? | | | Rather, I began with what is probably the oldest cipher still in active use, the polyalphabetic cipher, first described by Leon Battista Alberti in 1466, intending to adapt it for modern computer use. |
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http://www.contestcen.com/crypt003.htm
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| | Substitution cipher - Wikipedia, the free encyclopedia |
| | Between circa WWI and the widespread availability of computers (for some governments this was approximately the 1950s or 1960s; for other organizations it was a decade or more later; for individuals it was no earlier than 1975), mechanical implementations of polyalphabetic substitution ciphers were widely used. | | | From a sufficiently abstract perspective, modern bit-oriented block ciphers (eg, DES, or AES) can be viewed as substitution ciphers on an enormously large binary alphabet. | | | Provided the message is of reasonable length (see below), the cryptanalyst can deduce the probable meaning of the most common symbols by analysing the frequency distribution of the ciphertext—frequency analysis. |
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http://en.wikipedia.org/wiki/Substitution_cipher
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| | vigenere |
| | This cipher is well-known because while it is easy to understand and implement, it often appears to beginners to be unbreakable. | | | Consequently, many programmers have implemented obfuscation or encryption schemes in their applications which are essentially Vigenère ciphers, only to have them broken by the first cryptanalyst who comes along. | | | Kasiski actually used "superimposition" to solve the Vigenere cipher. |
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http://www.yourencyclopedia.net/vigenere.html
(1252 words)
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| | The Alberti Cipher |
| | The computer implements the cipher first by forming a plaintext-alphabet, and then a ciphertext-alphabet, which is based on a keyword. | | | Since the shift change is one of many factors that complicate solving a polyalphabetic cryptogram, a system for solving the cryptogram must be developed that works around the changing shift. | | | For Porta's type of cipher, the cryptographic key would consist of the permutation given in the first row of the table plus the shift that should be made after each letter of plaintext. |
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http://starbase.trincoll.edu/~crypto/historical/alberti.html
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| | Rotor machine |
| | In the mid-1400s, a new technique was invented by Alberti, now known generally as polyalphabetic ciphers, which recognised the virtue of using more than a single substitution alphabet; he also invented a simple technique for "creating" a multitude of substitution patterns for use in a message. | | | Monoalphabetic substitution ciphers used only a single replacement scheme — sometimes termed an "alphabet"; this could be easily broken, for example, by using frequency analysis. | | | By this means, a rotor machine produces a complex polyalphabetic substitution cipher. |
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http://www.worldhistory.com/wiki/R/Rotor-machine.htm
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| | CORE 139 S04: Lab 1 |
| | 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". | | | Each column thus represents a monoalphabetic cipher, and the index of coincidence can be computed for the column to verify this property. | | | S is the cipher alphabet used for the substitution cipher plus the value of k. |
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http://cs.colgate.edu/faculty/stina/courses/139/hw/lab1.html
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| | Cryptography -- Vigenere Cipher |
| | One of the main problems with simple substitution ciphers is that they are so vulnerable to frequency analysis. | | | Frequency analysis could then be used to solve the resulting simple substitutions. | | | So in fact the Gronsfeld is a weaker technique than Vigenere since it only uses 10 substitute alphabets (one per digit 0..9) instead of the 26 used by Vigenere. |
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http://www.trincoll.edu/depts/cpsc/cryptography/vigenere.html
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| | 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. | | | However, although imperfect, it is less so than the Gronsfeld cipher, and so the system might be of some use (although just converting to digits with a straddling checkerboard achieves the same goal, of simplifying applying a key, without any imperfections, and considerably more simply). | | | The table shown here can be thought of as a table for the addition of letters, which is equivalent to addition modulo 26, where A stands for 0, B stands for 1, continuing on to Z, which would stand for 25. |
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http://www.quadibloc.com/crypto/pp010303.htm
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| | Cipher Information and links |
| | Cipher is a complete development environment designed for creating state of the... | | | The operation of a cipher usually depends on a piece of auxiliary information, called a key or, in... | | | Cipher: The Newsletter of the IEEE Computer Society Technical Committee on Security and Privacy |
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http://www.seespyware.com/cipher.html
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| | CSI660T Programming Graduate Project |
| | For this project, the cipher used will be a straight Vigenere cipher, as described in class. | | | For example, it might read in the task file(s), use in-depth to guess the alignment(s) and key length, and then analyze the component simple substitution ciphers. | | | In this example, there are only three characters for each component simple substitution cipher. |
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http://www.cs.albany.edu/~berg/csi445/Assignments/project.html
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| | Lesson 0.5: Polyalphabetic Ciphers |
| | Frequency analysis was a devastating attack on monoalphabetic ciphers and they could no longer be considered secure. | | | The next development in cryptography was Polyalphabetic ciphers. | | | This example is not particularly memorable, but a word could be used as the master-key for method 2. |
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http://math.usask.ca/encryption/lessons/lesson00/page5.html
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| | Cryptography Tutorial - The Homophonic Cipher |
| | Although this is not a complete cryptanalysis it shows how an eavesdropper may gain information piece by piece to eventually break the whole cipher. | | | In addition to using computer assistance to find common di- and trigrams, he may use traditional cryptographic virtues such as gut instinct, logic and detective work to break secret messages. | | | 1) Understand how to encrypt, decrypt and break the Homophonic Cipher. |
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http://www.antilles.k12.vi.us/math/cryptotut/homophonic.htm
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| | Codes |
| | Keyword Cipher - This is an online, Java-Script enabled version of a Keyword cipher program, for you to try. | | | Caesar Cipher - This is an online, Java-Script enabled version of a Caesar cipher program, for you to try. | | | AutoKey Cipher - This is an online, Java-Script enabled version of an AutoKey cipher program, for you to try. |
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http://secretcodebreaker.com/codes.html
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| | Lanaki Lesson 11 |
| | When direct standard alphabets are used we can mechanically solve the cipher by completing the plain component. | | | In alphabets 2,3, and 5 the RSTplain sequence may be spotted at BCDcipher, ABCcipher, and CDEcipher, respectively, whereas in alphabet 4, if Ncipher = Eplain, then Ecipher = Nplain; therefore the original assumptions for the first halves will be confirmed by the goodness of fit of the distributions for the second halves. | | | The probable word method is very easy way to attack a Porta cipher. |
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http://www.fortunecity.com/skyscraper/coding/379/lesson11.htm
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| | cipher monoalphabetic Index - Computer-Technology-Find |
| | 0 bit cipher strength 128 bit cipher 5 cipher knowledge adfgvx cipher affine cipher algorithm cipher | | | Topics include email schemes and scams and general tips on using the Internet to avoid hackers and thiefs from stealing your personal information. A must read with safety tips for everyone on the Internet. | | | cipher vernam cipher vigenere cipher wheel cipher zero |
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http://www.computer-technology-find.com/Cipher/cipher-monoalphabetic.html
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| | sci.crypt: Re: Breaking polyalphabetic cipher.. |
| | In reply to: David Wilson: "Re: Breaking polyalphabetic cipher.." | | | Computers, however, can be a tremendous aid in solving ciphers, especially | | | Home > Newsgroups > sci.crypt > 2003-04 News Mailing-Lists Service UNIX / Linux / Coding / Shop / Directory Privacy |
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http://www.derkeiler.com/Newsgroups/sci.crypt/2003-04/1032.html
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| | BBC - h2g2 - Polyalphabetic Field Ciphers |
| | The Vigenère Cipher is much more secure than the Julius Caesar Cipher, nonetheless cryptanalysis was used to break it and the first person to successfully do so was none other than Charles Babbage, the spiritual father of computing. | | | As an example, assume the key was 'DOG'. | | | A Polyalphabetic Substitution Cipher is simply a cipher in which more than one alphabet is used. |
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http://www.bbc.co.uk/dna/h2g2/A583931
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| | Polyalphabetic substitution |
| | In the Beaufort cipher the table is used in the following way: | | | For an actual cryptosystem employing an unordered alphabet and Gronsfeld's system, see the page on the Swedish naval cipher of 1915. | | | One of the simplest polyalphabetic substitution ciphers is Gronsfeld's system. |
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http://hem.passagen.se/tan01/poly.html
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| | Vigenere Cipher |
| | Level: Finite mathematics, linear algebra, or a computer science course that includes a unit on cryptography. | | | An interactive Vigenere cipher routine is available in MATLAB, just click on ventable.ZIP. | | | For 300 years the Vigenere cipher was considered to be practically unbreakable. |
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http://astro.ocis.temple.edu/~dhill001/vigenere/vigenere.html
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| | Vigenere cipher - Infosecpedia |
| | In this tableau the input to the cipher are the lower case letters and the output is the uppercase lookup result. | | | A polyalphabetic cipher is built on the idea of simple substitution ciphers such as the Caeser cipher but uses multiple, rather than single, substitution alphabets. | | | Although the Vigenère cipher is named for Blaise de Vigenère, the cipher was invented by Giovan Batista Belaso, and a description of it was first published in in 1553. |
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http://infosecpedia.org/pedia/index.php/Vigenere_cipher
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| | Classical Cryptography: Substitution Ciphers |
| | Suppose that instead of always replacing the 'A' with 'D', one makes the replacement depend on where the letter appears in the message. | | | The key for this cipher can be any combination of letters, such as a word or phrase. | | | As it turns out, this system is not significantly harder to break than the Caesar cipher. |
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http://www.ece.utexas.edu/~gng/crypto/class_sub.shtml
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| | Information Assurance Student Group :: Mission Statement |
| | This time we'll venture a bit deeper (not too far). | | | Since the simple cipher went over extremely well, and to be honest are quite fun to play with- I decided to have a return in the cryptographic field. | | | You have until the end of Winter break to reply, then the answer will be posted. |
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http://iasg.ece.iastate.edu/Enigma/poly.html
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| | Polyalphabetic cipher - Wikipedia, the free encyclopedia |
| | The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case. | | | Alberti also invented a decoder device, his encryption disk, which implemented a cipher equivalent to the one published later by Johannes Trithemius. | | | Unlike Alberti's cipher, which switched alphabets at random intervals, Trithemius switched alphabets for each letter of the message. |
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http://en.wikipedia.org/wiki/Polyalphabetic_cipher
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| | vigenere.nb |
| | A brief description of these methods is presented, including a Java applet (with source code) which automates the solution of a Vigenere cipher. | | | 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. |
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http://mywebpages.comcast.net/erfarmer201/vigenere
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| | Learn more about Charles Babbage in the online encyclopedia. |
| | 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. | | | He broke Vigenère's autokey cipher as well as the much weaker cipher that is called Vigenère Cipher today. | | | Babbage's discovery was used to aid English military campaigns, and was not published until several years later; as a result credit for the development was instead given to Friedrich Kasiski, who made the same discovery some years after Babbage. |
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http://www.onlineencyclopedia.org/c/ch/charles_babbage.html
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| | Leone Battista Alberti - Open Encyclopedia |
| | Alberti was an accomplished cryptographer by the standard of his day, and invented both polyalphabetic ciphers and machine-assisted encryption using his cipher disk. | | | 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. | | | Cryptography historian David Kahn titles him the "Father of Western Cryptography", pointing to three significant advances in the field which can be attributed to Alberti: "the earliest Western exposition of cryptanalysis, the invention of polyalphabetic substitution, and the invention of enciphered code" (The Codebreakers, 1967). |
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http://open-encyclopedia.com/Leone_Battista_Alberti
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| | Dec1999 SC223 : Computer Security (Question 2)Suggested Solutions |
| | A polyalphabetic substitution cipher uses multiple mappings between plaintext and ciphertext, not just a single mapping. | | | A stream cipher encodes each letter as soon as it is input, whereas a block cipher encodes a whole block of letters at once (1 mark). | | | A good polyalphabetic cipher will have a flat frequency distribution, whereas the monoalphabetic cipher will have the same shaped frequency distribution as the plaintext (1 mark); hence the monoalphabetic cipher reveals information about the substitution mapping that the polyalphabetic cipher hides (1 mark). |
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http://www.informatics.edu.my/q-a/adcs/html/December99/sc223_d99q2s.htm
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| | [No title] |
| | The next example determines what the index of coincidence is for a polyalphabetic cipher for a large collection of letters. | | | Knowing what the value for the index of coincidence tells us, we now need to derive a formula for calculating it. | | | This leads to the following statement: Index of Coincidence Bound For a typical ciphertext message, the index of coincidence I satisfies: EMBED Equation.3 Fact: If I is close to 0.0385, then the cipher is likely to have been obtained from a polyalphabetic cipher. |
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http://www.runet.edu/~npsigmon/courses/cryptography/MWord/Section2.7notes.doc
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