I am trying to write a program in Java that uses Friedman Test. How can I write the algorithm? Is there any Java library for that?
Or you can try this too:
http://evilzone.org/java/(java)-cryptanalysis-friedman-test/
public class FriedmanTest implements Analysis {
//language is needed for the language specific IC
private Language language;
public FriedmanTest(Language language) {
this.language = language;
}
//returns the computed key length
@Override
public String analyse(String code) {
IndexOfCoincidence ic = new IndexOfCoincidence();
ic.analyse(code);
double kappaRandom = ic.computeKappaRandom();
double kappaText = ic.computeKappaText();
long n = code.length();
double kappaExpected = language.getIC() / ic.amountOfCharacters();
double keyLength = computeKeyLength(kappaRandom, kappaText,
kappaExpected, n);
return "computed key length: " + keyLength;
}
//uses the formula for the approximate key length
private double computeKeyLength(double kappaRandom, double kappaText,
double kappaExpected, long n) {
return ((kappaExpected - kappaRandom) * n)
/ ((n - 1) * kappaText - kappaRandom * n + kappaExpected);
}
}
public class FriedmanTest implements Analysis {
//language is needed for the language specific IC
private Language language;
public FriedmanTest(Language language) {
this.language = language;
}
//returns the computed key length
@Override
public String analyse(String code) {
IndexOfCoincidence ic = new IndexOfCoincidence();
ic.analyse(code);
double kappaRandom = ic.computeKappaRandom();
double kappaText = ic.computeKappaText();
long n = code.length();
double kappaExpected = language.getIC() / ic.amountOfCharacters();
double keyLength = computeKeyLength(kappaRandom, kappaText,
kappaExpected, n);
return "computed key length: " + keyLength;
}
//uses the formula for the approximate key length
private double computeKeyLength(double kappaRandom, double kappaText,
double kappaExpected, long n) {
return ((kappaExpected - kappaRandom) * n)
/ ((n - 1) * kappaText - kappaRandom * n + kappaExpected);
}
}
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