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A Fast Method for the Cryptanalysis of Substitution Ciphers
 Cryptologia
, 1995
"... It is possible to cryptanalyze simple substitution ciphers (both monoand polyalphabetic) by using a fast algorithm based on a process where an initial key guess is refined through a number of iterations. In each step the plaintext corresponding to the current key is evaluated and the result used as ..."
Abstract

Cited by 17 (1 self)
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It is possible to cryptanalyze simple substitution ciphers (both monoand polyalphabetic) by using a fast algorithm based on a process where an initial key guess is refined through a number of iterations. In each step the plaintext corresponding to the current key is evaluated and the result used as a measure of how close we are in having discovered the correct key. It turns out that only knowledge of the digram distribution of the ciphertext and the expected digram distribution of the plaintext is necessary to solve the cipher. The algorithm needs to compute the distribution matrix only once and subsequent plaintext evaluation is done by manipulating this matrix only, and not by decrypting the ciphertext and reparsing the resulting plaintext in every iteration. The paper explains the algorithm and it shows some of the results obtained with an implementation in Pascal. A generalized version of the algorithm can be used for attacking other simple ciphers as well. Keywords: Cryptanalysis,...
A Programmable Plaintext Recognizer
, 1994
"... Other researchers have studied the feasibility of a brute force attack on DES using several known plaintexts. In practice, known plaintext / ciphertext pairs may not be readily available, but statistical information about similar plaintexts is much more easily aquired. Accordingly, we design a stati ..."
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Cited by 4 (3 self)
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Other researchers have studied the feasibility of a brute force attack on DES using several known plaintexts. In practice, known plaintext / ciphertext pairs may not be readily available, but statistical information about similar plaintexts is much more easily aquired. Accordingly, we design a statistical plaintext recognizer suitable for use in a ciphertextonly key search machine. Software simulations indicate that this design gives a powerful attack on the encryption of lowentropy data.
The Automated Cryptanalysis of Analog Speech Scramblers
, 1998
"... An automated method of attacking commonIv used speech scramblers is presented. The cryptanalysis relies on the availability of the scrambled speech only and makes use of the characteristics of speech. It is shown that some of the currently available time and frequency domain scramblers, based on a f ..."
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An automated method of attacking commonIv used speech scramblers is presented. The cryptanalysis relies on the availability of the scrambled speech only and makes use of the characteristics of speech. It is shown that some of the currently available time and frequency domain scramblers, based on a fixed permutation, can be cryp. tanalysed. For systems where the permutation is changed with time, methods for partial recovery of the encrypted speech for several existing systems are given. In the case of the frequency domain scramblers a novel method of attack using a codebook is presented.
Evolving Keys for Periodic Polyalphabetic Ciphers
"... A genetic algorithm is used to find the keys of Type II periodic polyalphabetic ciphers with mixed primary alphabets. Because of the difficulty of the ciphertext only cryptanalysis for Type II ciphers, a multiphased search strategy is used, each phase of which recovers a bigger portion of the key. ..."
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A genetic algorithm is used to find the keys of Type II periodic polyalphabetic ciphers with mixed primary alphabets. Because of the difficulty of the ciphertext only cryptanalysis for Type II ciphers, a multiphased search strategy is used, each phase of which recovers a bigger portion of the key.