public string Analyze()
{
for (int a = 1; a < M; a++)
{
if (SimpleMaths.GCD(a, M) != 1)
{
continue;
}
for (int b = 0; b < M; b++)
{
AffineCipher affine = new AffineCipher(a, b);
string text = affine.DecryptText(cipherText);
double score = NgramStatistics.CountTextScore(text);
if (score > rate)
{
rate = score;
this.decryptedText = text;
}
}
}
return(decryptedText);
}
public string Analyze()
{
int size = (int)Math.Sqrt(text.Count);
for (int i = 0, period = 2; i < 10; i++, period++)
{
double ic = CountCoincidence(period);
lengths.Add(ic, period);
}
List <string> results = new List <string>();
string decryptedText = "";
double score = double.MinValue;
foreach (var length in lengths.Take(5))
{
int T = length.Value;
StringBuilder[] subs = new StringBuilder[T];
for (int i = 0; i < T; i++)
{
subs[i] = new StringBuilder();
}
for (int i = 0; i < text.Count; i++)
{
subs[i % T].Append(text[i]);
}
string[] decrypted = new string[T];
for (int i = 0; i < T; i++)
{
CaesarAnalyst analyst = new CaesarAnalyst(subs[i]);
decrypted[i] = analyst.Analyze();
}
StringBuilder str = new StringBuilder();
for (int i = 0; i < text.Count; i++)
{
str.Append(decrypted[i % T][i / T]);
}
double currentScore =
NgramStatistics.CountTextScore(str.ToString());
if (currentScore > score)
{
score = currentScore;
decryptedText = str.ToString();
}
}
return(decryptedText);
}
public string Analyze()
{
List <char> bestKey = FrequencySortedAlphabet(cipherText);
SimpleSubstitutionCipher cipher = new SimpleSubstitutionCipher(sortedAlphabet, bestKey);
string decryptedText = cipher.DecryptText(cipherText);
double score = NgramStatistics.CountTextScore(decryptedText);
for (int k = 0; k < 7; k++)
{
Random random = new Random();
parentKey = alphabet.Shuffle(random).ToList();
cipher = new SimpleSubstitutionCipher(alphabet, parentKey);
string text = cipher.DecryptText(cipherText);
rate = NgramStatistics.CountTextScore(text);
for (int t = 0; t < times; t++)
{
List <char> key = alphabet.Shuffle(random).ToList();
cipher = new SimpleSubstitutionCipher(alphabet, key);
string nextText = cipher.DecryptText(cipherText);
double currentRate = NgramStatistics.CountTextScore(nextText);
if (currentRate > rate)
{
parentKey = key;
text = nextText;
rate = currentRate;
for (int fail = 0; fail < 10000;)
{
int i = random.Next(alphabet.Count),
j = random.Next(alphabet.Count);
List <char> newKey = parentKey.Swap(i, j).ToList();
cipher = new SimpleSubstitutionCipher(alphabet, newKey);
string newText = cipher.DecryptText(cipherText);
double newRate = NgramStatistics.CountTextScore(newText);
if (newRate > rate)
{
parentKey = newKey;
text = newText;
rate = newRate;
fail = 0;
}
else
{
fail++;
}
}
}
}
if (rate > score)
{
score = rate;
decryptedText = text;
bestKey = parentKey;
}
}
return(decryptedText);
}
