hcrypto.analyzer
Class VigenereAnalyzer

java.lang.Object
  hcrypto.analyzer.CryptoAnalyzer
      hcrypto.analyzer.VigenereAnalyzer

All Implemented Interfaces:

Analyzer, ExpertAnalyzer, java.lang.Runnable

public class VigenereAnalyzer
extends CryptoAnalyzer
implements ExpertAnalyzer

Assumes that the text it is passed is encrypted with a Vigenere cipher. It performs both the Kasiski Test and the Superposition Analysis.

Field Summary

static int	MAX_BIGRAMS
static int	MAX_CONTACT
static int	MAX_FACTORS
static int	MAX_KEYWORD
static double	SUPERPOSNUMBER

Fields inherited from class hcrypto.analyzer.CryptoAnalyzer

PERMUTATION, PLAYFAIR, RAILFENCE, SIMPLESUB

Fields inherited from interface hcrypto.analyzer.Analyzer

DECIPHER_LIMIT

Constructor Summary

VigenereAnalyzer()

VigenereAnalyzer(AnalyzerFrame f)

VigenereAnalyzer(TextStatistics ts)

Method Summary

void	computeBigramDistances(java.lang.String s)
void	computeSuperpositionAnalysis(java.lang.String s) This method performs a superposition test.
void	doAnalysis()
void	doAnalysis(java.lang.String s)
java.lang.String	estimateKeyword(int keyLen) To find the find the keyword we break the cryptogram into keyLen monoalphabetic cryptograms, each of which is obtained by a Caesar shift from the standard alphabet.
int	estimateKeywordLength(int[] factors)
java.lang.String	getKeywordString()
int	getOptimalShift(int firstChar, int displ) This method performs a Chi-Square test to find the optimal Caesar shift on a polyalphabetic text.
java.lang.String	getReport() Part of Analyzer interface.
void	run() Part of Analyzer and Runnable interface.
void	setup(java.lang.String s) setup() initializes the text and the result string.

Methods inherited from class hcrypto.analyzer.CryptoAnalyzer

prettyPrint, setup, stopThread, threadIsStopped, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

MAX_BIGRAMS

public static final int MAX_BIGRAMS

See Also:

Constant Field Values

MAX_FACTORS

public static final int MAX_FACTORS

See Also:

Constant Field Values

MAX_KEYWORD

public static final int MAX_KEYWORD

See Also:

Constant Field Values

MAX_CONTACT

public static final int MAX_CONTACT

See Also:

Constant Field Values

SUPERPOSNUMBER

public static final double SUPERPOSNUMBER

See Also:

Constant Field Values

Constructor Detail

VigenereAnalyzer

public VigenereAnalyzer()

VigenereAnalyzer

public VigenereAnalyzer(AnalyzerFrame f)

VigenereAnalyzer

public VigenereAnalyzer(TextStatistics ts)
                 throws java.lang.NullPointerException

Throws:

java.lang.NullPointerException

Method Detail

setup

public void setup(java.lang.String s)

Description copied from class: CryptoAnalyzer

setup() initializes the text and the result string. Note that for files containing test cryptograms, the solution is sometimes also provided following the $$$ marker.

Specified by:

setup in interface Analyzer

Overrides:

setup in class CryptoAnalyzer

run

public void run()

Description copied from class: CryptoAnalyzer

Part of Analyzer and Runnable interface. Override this method in the subclass.

Specified by:

run in interface Analyzer

Specified by:

run in interface java.lang.Runnable

Overrides:

run in class CryptoAnalyzer

getReport

public java.lang.String getReport()

Description copied from class: CryptoAnalyzer

Part of Analyzer interface.

Specified by:

getReport in interface Analyzer

Overrides:

getReport in class CryptoAnalyzer

computeSuperpositionAnalysis

public void computeSuperpositionAnalysis(java.lang.String s)

This method performs a superposition test. It places the original text on one line and superposes a copy of the text, displaced by 1..MAX_KEYWORD positions, under the original text. Then it computes the number of coincidences that result between the two lines.

computeBigramDistances

public void computeBigramDistances(java.lang.String s)

getKeywordString

public java.lang.String getKeywordString()

Specified by:

getKeywordString in interface ExpertAnalyzer

doAnalysis

public void doAnalysis(java.lang.String s)

Specified by:

doAnalysis in interface ExpertAnalyzer

doAnalysis

public void doAnalysis()

estimateKeywordLength

public int estimateKeywordLength(int[] factors)

estimateKeyword

public java.lang.String estimateKeyword(int keyLen)

To find the find the keyword we break the cryptogram into keyLen monoalphabetic cryptograms, each of which is obtained by a Caesar shift from the standard alphabet. So for each letter in the keyword, find its shift.

getOptimalShift

public int getOptimalShift(int firstChar,
                           int displ)

This method performs a Chi-Square test to find the optimal Caesar shift on a polyalphabetic text. It assumes that every _displ_ character starting at _firstChar_ belongs to the same alphabet. It is used primarily for analyzing Vigenere-like and Caesar-shift cryptograms.

Parameters:

firstChar - - the location of the first character in the cryptotext

displ - - the displacement (keyword length) or cycle length