hcrypto.analyzer.evolutionary
Class NgramGaAnalyzer

java.lang.Object
  hcrypto.analyzer.CryptoAnalyzer
      hcrypto.analyzer.evolutionary.GaAnalyzer
          hcrypto.analyzer.evolutionary.NgramGaAnalyzer

All Implemented Interfaces:

Analyzer, java.lang.Runnable

public class NgramGaAnalyzer
extends GaAnalyzer

Assumes that the text is encrypted with simple substitution cipher and uses a frequency-based genetic algorithm to analyze it.

Its evaluation function uses an NgramArray with frequencies of N = 2, 3, or 4 (bigrams, trigrams, or tetragrams) to cryptanalyze transposition and substitution ciphers. Using the sum of the inverses of the frequencies as an evaluation of how accurately a decrypt matches the usual N-gram frequencies in a language is an idea described by Alex Griffing the developer of the "Automatic Cryptogram Solver". This program is based on R. Walde's NgramClimber.java. To compile and run from the TestAnalyzer application: cd ~crypto/hcryptoj/1.4/applications/testanalyzer javac -classpath ../../classes -d ../../classes ../../source/hcrypto/analyzer/NgramGaAnalyzer.java java -classpath ../../classes:. TestAnalyzer analyzers.NgramAnalyzer ga_paramfiles ngram.ga.cgrams.txt

Field Summary

Fields inherited from class hcrypto.analyzer.CryptoAnalyzer

PERMUTATION, PLAYFAIR, RAILFENCE, SIMPLESUB

Fields inherited from interface hcrypto.analyzer.Analyzer

DECIPHER_LIMIT

Constructor Summary

NgramGaAnalyzer()
NgramGaAnalyzer() -- Default constructor

NgramGaAnalyzer(GaParameters params, AnalyzerFrame f)
NgramGaAnalyzer() -- this constructor is given an object containing parameter settings

Method Summary

void	run() run() conducts the GA run and reports the results.
void	setup(java.lang.String text) setup() creates the population for the NgramGa.

Methods inherited from class hcrypto.analyzer.CryptoAnalyzer

getReport, prettyPrint, setup, stopThread, threadIsStopped, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

NgramGaAnalyzer

public NgramGaAnalyzer()

NgramGaAnalyzer() -- Default constructor

NgramGaAnalyzer

public NgramGaAnalyzer(GaParameters params,
                       AnalyzerFrame f)

NgramGaAnalyzer() -- this constructor is given an object containing parameter settings

Parameters:

params - -- an object containing param1=val1 param2=val2 ...

g - -- the AnalyzerFrame (GUI) for this analyzer

Method Detail

setup

public void setup(java.lang.String text)

setup() creates the population for the NgramGa.

Specified by:

setup in interface Analyzer

Overrides:

setup in class GaAnalyzer

run

public void run()

run() conducts the GA run and reports the results.

Specified by:

run in interface Analyzer

Specified by:

run in interface java.lang.Runnable

Overrides:

run in class GaAnalyzer