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Topic: Monoalphabetic substitution cipher

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Simple substitution cipher

Substitution cipher

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Caesar cipher

Polyalphabetic substitution

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Autokey cipher

Product cipher

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	Codes, Ciphers, & Codebreaking (Site not responding. Last check: 2007-11-03)
		Use of ciphers for military purposes goes back at least to Julius Ceasar, who was skilled in their use.
		This large number of possible monoalphabetic substitution cipher alphabets means that if such a "mixed cipher alphabet" is used, cracking it with a brute-force attack is very difficult.
		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.
	www.darkmattermag.com /October2003/dark_science2.htm (679 words)

	[2.0] Refining The Art
		For example, two substitution cipher alphabets could be defined and used on alternating letters of a plaintext, with all the even-numbered letters enciphered by one cipher alphabet and all the odd-numbered letters enciphered by the other.
		In principle, a homophonic substitution cipher could be designed so that none of the the symbols in the ciphertext would have a frequency greater than 1%, defeating frequency analysis.
		Poe was actually fairly knowledgeable about codes and ciphers, and had something of a reputation as a "genius" for his ability to crack monoalphabetic substitution ciphers from ciphertexts submitted to him by readers.
	www.vectorsite.net /ttcode_02.html (3082 words)

	Free2Code - articles - Cipher Tutorial
		Cipher is a general term and means a combination of symbols representing an encoded version of something legible.
		A transposition cipher is is a cipher in which the letters of the plaintext remain unchanged, but are shuffled around according to a specific set of rules, for example in a columnar 5x10 transposition cipher:
		A coumnar cipher is generally easy to discover due to the fact that the frequency of the letters remains constant to your native languages' frequency.
	www.free2code.net /plugins/articles/read.php?id=7 (543 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.
		monoalphabetic substitution cipher : A substitution cipher in which the cipher alphabet is fixed throughout encryption.
		substitution cipher : A system of encryption in which each letter of a message is replaced with another character, but retains its position within the message.
	members.fortunecity.com /templarser/cipherglos.html (1226 words)

	Monoalphabetic Cipher (Site not responding. Last check: 2007-11-03)
		Ciphers in which the cipher alphabet remains unchanged throughout the message are called Monoalphabetic Substitution Ciphers.
		If we permit the cipher alphabet to be any rearrangement of the plain alphabet, then we can generate an enormous number of distinct modes of encryption.
		If our message is intercepted by the enemy, who correctly assumes that we have used a monoalphabetic substitution cipher, they are still faced with the impossible challenge of checking all possible keys.
	www.simonsingh.net /The_Black_Chamber/generalsubstitutionWithMenu.html (177 words)

	cipher monoalphabetic Index - Computer-Technology-Find (Site not responding. Last check: 2007-11-03)
		The Monoalphabetic Cipher (often referred to as a cryptogram) uses a KEY which...
		Monoalphabetic Substitutions A monoalphabetic substitution is a cipher in which each occurrence of a plaintext sym- bol is...
		The Caesar Shift Cipher is one example of a Monoalphabetic Cipher.
	www.computer-technology-find.com /Cipher/cipher-monoalphabetic.html (527 words)

	[5.0] The Mechanization of Ciphers
		The simple "cipher disk" goes back to the 15th Century, when it was invented by Leon Alberti, one of the fathers of the polyalphabetic substitution cipher.
		The cipher disk reduces the labor of using a Vigenere cipher, and remained in use for centuries.
		The drawback is that the the cipher is much more predictable, since the sequence of different substitution alphabets is fixed, though Alice can change the starting point of the sequence by setting the rotor to one of its 26 possible initial positions.
	www.vectorsite.net /ttcode_05.html (6516 words)

	Cracking Substitution Cipher
		The monoalphabetic substitution cipher seemed uncrackable, because of the huge number of possible keys.
		The cracking of the substitution cipher marks the birth of cryptanalysis (code breaking).
		Although it is not known who first realized that the variation in the frequencies of letters could be exploited in order to break ciphers, the earliest known description of the technique is by the 9th century scientist Abu Yusuf Ya 'qub ibn Is-haq ibn as-Sabbah ibn 'omran ibn Ismail al-Kindi.
	www.simonsingh.net /The_Black_Chamber/crackingsubstitution.html (346 words)

	Iang's Library - Simon Singh - The Code Book - The Arab Cryptanalysts
		The administrators usually employed a cipher alphabet which was simply a rearrangement of the plain alphabet, as described earlier, but they also used cipher alphabets that contained other types of symbols.
		The monoalphabetic substitution cipher is the general name given to any substitution cipher in which the cipher alphabet consists of either letters or symbols, or a mix of both.
		If the entire book were encrypted via a monoalphabetic substitution cipher, then a naive attempt to deciper it might be stymied by the complete lack of the most frequently occurring letter in the English alphabet.
	iang.org /crypto_fiction/singh_the_arab_cryptanalysts.html (1567 words)

	Monoalphabetic Substitution Cipher Applet (Site not responding. Last check: 2007-11-03)
		The letters A-Z are substituted according to the characters specified in the "Cipher alphabet".
		The cipher alphabet present when the applets starts up implements a "Caesar-shift" substitution cipher, whereby the normal, in this case English, alphabet is "shifted" a certain number of places to the right.
		The Caesar-shift substitution cipher was used by Julius Caesar to deliver secret messages, for example, to Cicero.
	www.reed.edu /~mcphailb/applets/crypto (200 words)

	Cryptosystems and Keys
		Any monoalphabetic substitution cipher can be broken by comparing the relative frequencies of occurrence of the letters in intercepted ciphertext samples with the corresponding statistics for letters in plaintext examples of related writings.
		You could sequentially use the letters of a key word as key letters for monoalphabetic substitution of sequential plaintext letters from separate substitution alphabets, equal in number to the number of letters in the key.
		This polyalphabetic substitution cipher blurs the statistics of the letter frequencies to an almost flat probability distribution.
	www.cerberussystems.com /INFOSEC/tutorial/keys.htm (2222 words)

	Basic Cryptography
		The monoalphabetic substitution cipher involves replacing each letter of the alphabet with a different letter coming from a shifted set of letters.
		In order to easily break a monoalphabetic substitution cipher some knowledge of the language must be known, such as the relative frequency of of letters.
		Naturally enough the next ciphered letter is the intersection of the 'i' row and 'e' column with produces 'M'.
	www.bletchleypark.net /cryptology/Basic_Cryptography.html (702 words)

	Example of Breaking a Substitution
		An Example of Breaking a Monoalphabetic Substitution Cipher
		Examining the keyword substitution list, we clearly see the end of the alphabet in place.
		This would force us to associate s with P and z with Y. The spacing would require that q is associated with either M or N, but the low frequency of "q" favors the association of q with N. letter frequency count, and digram and trigram count.
	www-math.cudenver.edu /~wcherowi/courses/m5410/exsubcip.html (636 words)

	Dragon Crypto: Day 1
		A monoalphabetic substitution cipher replaces every letter in the plaintext message with a substitute letter in the ciphertext.
		If you were able to break the cipher in question 3, you know that a monoalphabetic substitution cipher is not very secure.
		The Vigenere Cipher is like the Caesar Cipher, but instead of using the same key for each letter, it uses a word as the key and cycles through the different letters in the key word.
	www.cs.virginia.edu /~evans/dragoncrypto/day1.html (707 words)

	CS 513 System Security -- Introduction to Cryptography
		Another--somewhat stronger, cryptographically--example of a monoalphabetic substitution cipher is to use an arbitrary permutation of the alphabet, rather than shifting by a certain number.
		Therefore, if we know the original language, and we know that a monoalphabetic substitution was used, then we have a good chance of cracking the code.
		The problem with monoalphabetic substitution ciphers is that the preservation of alphabet distributions makes them vulnerable to frequency-based attacks.
	www.cs.cornell.edu /Courses/cs513/2000SP/L23.html (1254 words)

	Polyalphabetic Substitution Ciphers
		The only difference to the Vigenere cipher is the use of the table: Locate the plain text letter in the first column and trace in the row to the key letter.
		For this variant of the Beaufort cipher, the role of the key and plain text letters are exchanged.
		As for the other polyalphabetic substitution ciphers you may choose one of the operation modes.
	members.aon.at /cipherclerk/Doc/Vigenere.html (839 words)

	Monoalphabetic Substitution Cipher (Site not responding. Last check: 2007-11-03)
		The next type of cipher is the mono-alphebetic substitution cipher.
		In this type of cipher each letter is represented always as a certain letter, which could be itself (in the example Z is encrypted as itself).
		Once a few letters have been worked out they can be put back into the cipher text and then susequent letters can then be worked out since you are able to guess at some words.
	www.bath.ac.uk /~ma3ljb/mono.html (227 words)

	Dec1999 SC223 : Computer Security (Question 2)Suggested Solutions (Site not responding. Last check: 2007-11-03)
		In a monoalphabetic substitution cipher, each letter of the plaintext is replaced with a single letter of ciphertext (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).
		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).
	www.informatics.edu.my /q-a/adcs/html/December99/sc223_d99q2s.htm (649 words)

	MonoAlphabetic Substitution Cipher : Part 5 of a Series
		MonoAlphabetic Substitution Cipher written in C. Ok, I almost made the mistake of bypassing this cipher.
		The next function we encounter is once also common to all previous examples, it is the routine used to find the length of a file using fseek() and ftell().
		Even transposition won't really increase the strength of the monoalphabetic substitution part of the cipher if the attack is based upon simple frequency analysis.
	www.osix.net /modules/article?id=561&topicextend=1 (1331 words)

	Practicum #2, Math 133 (Site not responding. Last check: 2007-11-03)
		A monoalphabetic substitution cipher is a process for obscuring a message by replacing each letter of the alphabet with a different letter.
		This is the "substitution" part of the name, the "monoalphabetic" means just one set of substitutions is used, and remains the same throughout the encoding of the message.
		Use the space bar to see different ways of arranging the two alphabets (cipher frequency is the best).
	buzzard.ups.edu /courses/2003fall/practicum02.html (365 words)

	Button Instructions (Site not responding. Last check: 2007-11-03)
		In any cipher the first thing to do is get the frequency analysis of the characters in the cipher.
		Cypher defaults to monoalphabetic substitution cipher as the cipher guessed in use.
		Transposition ciphers are a means by which the position of the letters is changed.
	www.cs.unc.edu /Courses/145/homes/crypt/userManual/user_button.html (382 words)

	sci.crypt: Re: manual cryptography
		Re: im still trying to get the grips of monoalphabetic substitution.
		is usually a monoalphabetic cipher with a key word used...
		Cipher: c k v e b o y f d
	www.derkeiler.com /Newsgroups/sci.crypt/2003-12/0122.html (389 words)

	Dec1999 SC223 : Computer Security (Question 2) (Site not responding. Last check: 2007-11-03)
		What is it that makes a polyalphabetic substitution cipher more secure than a monoalphabetic cipher?
		Explain the difference between a block cipher and a stream cipher.
		It is English text, encrypted using a monoalphabetic cipher.
	www.informatics.edu.my /q-a/adcs/html/December99/sc223_d99q2.htm (89 words)

	Security Glossary
		Official documents and tax records were at that time protected by cipher alphabets which included other symbols as well as letters.
		So, if the language of the enciphered text is known, then cryptanalysts will first try substituting the most frequently occurring letter in the text by the most frequently occuring letter in the language, and then the second, and so on.
		If substituting the most frequent letter in the language does not make sense, then the second most frequent is tried, and so on.
	ourworld.compuserve.com /homepages/sNethercott/SecurityGlossM.html (303 words)

	Monoalphabetic Substitution Cipher Solver
		The Monoalphabetic Cipher (often referred to as a cryptogram) uses a KEY which is the rearrangement of the letters of the alphabet.
		These different letters are then substituted for the letters in the message to create a secret message.
		A program written by Chris Card that can determine the KEY and break most secret messages that have been enciphered using a Monoalphabetic Cipher.
	secretcodebreaker.com /scbsolvr.html (182 words)

	Assignment 2 (Site not responding. Last check: 2007-11-03)
		In order to make things more difficult for Eve, Alice and Bob decide to perform a double encryption as follows: First, they encrypt the plaintext using a Caesar shift and then they encrypt the resulting ciphertext using a monoalphabetic substitution cipher.
		Is this system more secure, less secure or about the same as a single encryption using a monoalphabetic substitution cipher?
		Vigenere is associated with the autokey method of generating long keys for enciphering using the Vigenere table.
	dkrizanc.web.wesleyan.edu /courses/133/04/assign2.html (305 words)

	CORE 139 S04: Cipher Tools (Site not responding. Last check: 2007-11-03)
		Display all of the additive shifts of a text, with counts of the high and low frequency letters in each shift
		Guess cipher alphabet and/or plaintext letters to decrypt a monoalphabetic substitution cipher
		Count letter, digraph, and trigraph frequencies plus letter contacts (how often a letter occurs before and after other letters)
	cs.colgate.edu /faculty/nevison/Core139Web/tools (217 words)

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