public Tuple <string, string, double> Decipher(string code = "")
{
Stopwatch s = new Stopwatch();
s.Start();
if (code != "")
{
Code = code;
}
string key = CipherGenerator.CreateRandomKey();
string betterKey = key;
string bestKey = key;
double betterFitness = CalcFitness(Code);
double bestFitness = betterFitness;
double words;
int first = 0, sec = 0, tries = 0;
bool hasBetterFitness;
//Check a bunch of similar keys, changing a little each time
do
{
do
{
hasBetterFitness = false;
key = betterKey;
for (first = 0; first < key.Length - 1; first++)
{
for (sec = first; sec < key.Length; sec++)
{
//Swap two letters
string testKey = sec == first ? key : Swap(key, first, sec);
Cipher c = new Cipher(testKey);
Cleartext = c.Decode(Code);
//Check if it's English
double fitness = CalcFitness(Cleartext);
if (fitness < betterFitness)
{
//Use the better key as a base key
betterFitness = fitness;
betterKey = testKey;
hasBetterFitness = true;
}
}
}
}while (hasBetterFitness);
if (betterFitness < bestFitness)
{
bestFitness = betterFitness;
bestKey = betterKey;
}
else
{
tries++;
}
betterKey = CipherGenerator.CreateRandomKey();
key = bestKey;
Cipher cipher = new Cipher(key);
Cleartext = cipher.Decode(Code);
//Check agaainst a dictionary to avoid local maxima
words = CountGoodWords(KeepWords(Cleartext, " "));
betterFitness = CalcFitness(Cleartext);
if (tries > 10)
{
bestFitness = 10;
tries = 0;
}
}while (words > 0.12);
s.Stop();
var time = s.Elapsed;
return(Tuple.Create(Cleartext, key, bestFitness));
}
public void GenerateCipherPair(RandomGenerator random, out StatementBlock encrypt, out StatementBlock decrypt)
{
CipherGenerator.GeneratePair(random, out encrypt, out decrypt);
}
