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Topic: Simple substitution cipher

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Monoalphabetic substitution cipher

Substitution cipher

Caesar cipher

Hill cipher

Ciphertext

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	Substitution cipher - Wikipedia, the free encyclopedia
		In cryptography, a substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth.
		By contrast, in a substitution cipher, the units of the plaintext are retained in the same sequence in the ciphertext, but the units themselves are altered.
		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.
	en.wikipedia.org /wiki/Substitution_cipher (2649 words)

	Caesar cipher - Wikipedia, the free encyclopedia
		It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions further down the alphabet.
		Even as late as 1915, the Caesar cipher was in use: the Russian army employed it as a replacement for more complicated ciphers which had proved to be too difficult for their troops to master; German and Austrian cryptanalysts had little difficulty in decrypting their messages.
		In the first case, the cipher can be broken using the same techniques as for a general simple substitution cipher, such as frequency analysis or pattern words.
	en.wikipedia.org /wiki/Caesar_cipher (1361 words)

	Substitution cipher (Site not responding. Last check: 2007-10-20)
		The simple substitution cipher is one in which each plaintext character is simply replaced by a corresponding one from a cipher alphabet.
		The cipher alphabet may be shifted or reversed (creating the Caesar cipher and atbash ciphers, respectively) or scrambled, in which case it is called a "mixed alphabet" or "deranged alphabet".
		Unfortunately, the Hill cipher is vulnerable to a known plaintext attack because it is completely linear, so it must be combined with some non-linear step to defeat this attack.
	www.sciencedaily.com /encyclopedia/substitution_cipher (2397 words)

	Substitution cipher (Site not responding. Last check: 2007-10-20)
		The simple substitution cipher is one in which each plaintext character issimply replaced by a corresponding one from a cipher alphabet.
		Polyalphabetic substitution ciphers were firstdescribed in 1467 by Leone Battista Alberti in the form of disks.
		Modern stream ciphers can also be seen, from a sufficiently abstractperspective, to be a form of polyalphabetic cipher in which all the effort has gone into making the keystream as long andunpredictable as possible.
	www.therfcc.org /RFCC/substitution-cipher-72540.html (2106 words)

	Playfair cipher - Wikipedia, the free encyclopedia
		The Playfair cipher or Playfair square is a manual symmetric encryption technique and was the first literal digraph substitution cipher.
		The Playfair is thus significantly harder to break since the frequency analysis used for simple substitution ciphers does not work with it.
		When only the ciphertext is known, brute force cryptanalysis of the cipher involves searching through the key space for matches between the frequence of occurrence of digrams (pairs of letters) and the known frequency of occurrence of digrams in the assumed language of the original message.
	en.wikipedia.org /wiki/Playfair_cipher (1085 words)

	Substitution Ciphers
		Substitution Ciphers are ciphers in which each letter is replaced by a different letter.
		Typically in a homophonic substitution cipher, the cipher alphabet (the symbols which can appear in a ciphertext) is larger than the plaintext alphabet.
		Polygram substitution ciphers are ciphers in which ciphertext polygrams (sequences of a few letters) are substituted for plaintext polygrams.
	www.disappearing-inc.com /S/substitutionciphers.html (657 words)

	Soviet Simple Substitution Cipher (Site not responding. Last check: 2007-10-20)
		This is a worksheet from the FRA archive, showing a recovered key for a simple substitution cipher used on September 1st, 1944 by two Soviet radiostations giving the call signs 8HZ and GKF.
		Apparently this cipher looked like a 5-figure system when intercepted, and on the top of the worksheet - barely visible - we are told that positions 1, 2, and 4 in a group are dummies, so that a group such as 01012 simply means 02, or "period".
		Once the trick with the dummy figures were found out, this cipher is simply a variant of Caesar's cipher, using figures instead of letters.
	hem.passagen.se /tan01/Arch/sovsimp.htm (188 words)

	Playfair cipher (Site not responding. Last check: 2007-10-20)
		The Playfair cipher or Playfair square is a manual symmetric encryption technique invented in 1854 by Charles Wheatstone for telegraph secrecy and was the first literal digraph substitution cipher.
		Memorization of the key and 4 simple rules was all that was required to create the 5 by 5 table and use the cipher.
		When only the ciphertext is known, cryptanalysis of the cipher involves searching through the key space for matches between the frequence of occurrence of digrams (pairs of letters) and the known frequency of occurrence of digrams in the language of the original message.
	www.sciencedaily.com /encyclopedia/playfair_cipher (900 words)

	[1.0] Introduction To Codes, Ciphers, & Codebreaking (Site not responding. Last check: 2007-10-20)
		This is a simple cipher algorithm, but even if a codebreaker knows that this general scheme was used, the message still cannot be read without the key, and a brute-force approach to cracking it is very difficult.
		The ancient Spartans used a form of transposition cipher, in which a strip of parchment was wound in a spiral around a wooden cylinder known as a "scytale", and a message was written down the length of the cylinder.
		The frequency of the cipher letters of course is the frequency of their plaintext equivalents, and so at first sight it would be logical to believe that the ciphertext "O" at the top of the list corresponds to plaintext "e", while the ciphertext "N" at the bottom of the list corresponds to plaintext "z".
	www.vectorsite.net /ttcode1.html (4833 words)

	CSA: Glossary (Site not responding. Last check: 2007-10-20)
		The well-known Caesar shift is a simple substitution cipher wherein the ciphertext is made from the plaintext by substituting for each letter the one three places to the right in the alphabet, modulo 26: A becomes D, Y becomes B, M becomes P, and so on.
		In the case of a simple substution cipher, ciphertext is made from a clear message (the plaintext) by translating, using a key, the letters of the words one letter at a time.
		In the case of a simple substution cipher, plaintext is made from ciphertext by translating, using a deciphering key, the letters of the words one letter at a time.
	home.hiwaay.net:8000 /~kdunn/problems/csa_help/csah_glo.html (437 words)

	Chapter 9 -- ACA Jargon and Familiar Terms
		Cipher Exchange - a department of the Cm containing a variety of cipher types.
		Code - A special form of substitution cipher in which letters, words, phrases or even whole sentences are replaced by groups of characters chosen arbitrarily.
		Simple Substitution - a cipher in which each letter of the Pt is replaced by one cipher letter, the replacements being unique and no letter standing for itself.
	www.cryptogram.org /cdb/aca.info/aca.and.you/chap09.html (546 words)

	Cryptography -- Vigenere Cipher (Site not responding. Last check: 2007-10-20)
		One of the main problems with simple substitution ciphers is that they are so vulnerable to frequency analysis.
		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)

	Encyclopedia article on Cryptanalysis [EncycloZine] (Site not responding. Last check: 2007-10-20)
		For example, in a simple substitution cipher (where each letter is simply replaced with another), the most frequent letter in the ciphertext would be a likely candidate for "E".
		In academia, new designs are regularly presented, and are also frequently broken: the 1984 block cipher Madryga was found to be susceptible to ciphertext-only attacks in 1998; FEAL-4, proposed as a replacement for the DES standard encryption algorithm, was demolished by a spate of attacks from the academic community, many of which are entirely practical.
		In industry, too, ciphers are not free from flaws: for example, the A5/1, A5/2 and CMEA algorithms, used in mobile phone technology, can all be broken in hours, minutes or even in real-time using widely-available computing equipment.
	encyclozine.com /Cryptanalysis (2230 words)

	Simple Substitution
		The most simple crypto systems only substitute the plaintext letters for other letters, numbers, or, in some cases, arbitrary symbols.
		To encrypt a text with this crypto, the letters of the plaintext are substituted for two-figure numbers, the first figure of every number telling in which row the plaintext letter stands, and the last figure telling the column.
		The idea of the simpler checkerboard cipher just described, together with a Caesar-like crypto were to some extent used by the old Vikings.
	hem.passagen.se /tan01/simsub.html (1467 words)

	IC2: Unit 4 Exercises (Site not responding. Last check: 2007-10-20)
		Show that, for a Caesar Cipher, encrypting with key k is the same as decrypting with key 26-k.
		If a Simple Substitution Cipher is used (with an unknown key) and you intercept the ciphertext OXAO then explain why you can be confident that the plaintext is not JOHN.
		The Vigenère Cipher was described in Piper and Murphy as using a key word with no repeated letters.
	www.isg.rhul.ac.uk /msc/teaching/ic2/exercises04/Unit4exercises.shtml (709 words)

	CME's Cryptography Timeline (Site not responding. Last check: 2007-10-20)
		The cipher is a simple substitution with a cipher alphabet consisting of letters, digits and symbols.
		He invented a steganographic cipher in which each letter was represented as a word taken from a succession of columns.
		It was a practical public-key cipher for both confidentiality and digital signatures, based on the difficulty of factoring large numbers.
	world.std.com /~cme/html/timeline.html (3709 words)

	NOVA Online \| Decoding Nazi Secrets \| A Simple Cipher
		A cipher, on the other hand, is a message in which letters or symbols replace the actual letters in the message.
		The key for a cipher used by Augustus Caesar, some 2,000 years ago, was simple enough: The receiver just had to shift the alphabet one position.
		The cipher's key is straightforward -- each letter of the alphabet is represented by another letter.
	www.pbs.org /wgbh/nova/decoding/break.html (197 words)

	Simple Substitution Ciphers
		All a Simple Substitution Cipher does is replace one letter of the alphabet with another letter according to some pre-arranged system.
		This second problem is the fact that a Simple Substitution cipher is vulnerable to the type of frequency analysis described here.
		So this simple example shows the caution that has to be employed when choosing a cipher system, you can't just rely on the fact that it has a large number of keys to ensure its security.
	people.bath.ac.uk /tab21/simplesub.html (597 words)

	What are substitution and transposition ciphers?
		An even more complex substitution cipher can be made by having each character of the alphabet correspond to a different letter of the alphabet, without a set pattern.
		The Vernam Cipher, or one time pad, is a simple substitution cipher where the key length equals the message length.
		ROT-13 is a simple substitution cipher used to encode messages on Usenet.
	www.tech-faq.com /substitution-transposition-cipher.shtml (345 words)

	The Legend of Poe the Cryptographer
		Other ciphers were also rejected because they did not fall into the simple substitution category Poe gave as a condition for the challenge (Wimsatt 761).
		In both instances, Poe challenged the public with a "simple substitution" cipher, but the way he proposed the challenges deceived the readers into thinking the cryptology involved was more difficult than the solution actually required.
		The substitution of characters, "however unusual or arbitrary," as Poe says to seemingly complicate the challenge and thus impress his readership, in fact makes no difference to the decipherer.
	www.usna.edu /EnglishDept/poeperplex/cryptop.htm (1648 words)

	Poe and Cryptography
		A simple substitution cipher is one in which the same symbol stands for the same letter of the alphabet in the concealed message.
		In addition, Poe appears to have solved a cipher which some symbols to stand for more than one letter of the plain text and in one case a cipher in which 7 different alphabets were used.
		In this last case, since we don't have the cipher text itself, it is believed that a new alphabet was used on each line of the plain text, rather than a cipher such as Vigenere's.
	starbase.trincoll.edu /~crypto/historical/poe.html (689 words)

	Xtreme Visual Basic Talk - Simple Encryption
		A cipher is a way of scrambling a message in such a way that the original message can be unscrambled.
		One of the first ciphers was a simple shift algorithm used by Julius Caesar.
		The vignere cipher is similar to a series of substitution ciphers.
	www.visualbasicforum.com /t31778.html (1961 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		INSTRUCTIONS FOR THE SIMPLE SUBSTITUTION CIPHER KEY 1 CREATOR This program has been provided for the user's entertainment and can be used freely and modified as the user wishes.
		That is, is there a plain alphabet letter represented by itself in the cipher alphabet.
		The keyed plain alphabet and straight cipher alphabet with proper shift will be displayed as well as the plaintext, the ciphertext, the crib (if any) and its caesar encipherment.
	www.und.nodak.edu /org/crypto/crypto/solvers/dutchman/HelpSS1.txt (661 words)

	Security Information » Blog Archive » Simple Substitution Cipher Tools (Site not responding. Last check: 2007-10-20)
		Simple Substitution Cipher Tools: “We have searched through the details and sifted it so that it will be convenient for you.
		We have been seeking tons of top resources on the matter of simple substitution cipher tools and we have discovered there is good reporting and low quality reporting.
		This research about simple substitution cipher tools was built to be significant and significant.
	www.securityweblog.com /simple-substitution-cipher-tools (104 words)

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