public string Analyse3By3Key(string plainText, string cipherText)
{
//throw new NotImplementedException();
MatrixOP r = new MatrixOP();
Dictionary <char, int> DT = new Dictionary <char, int>();
Dictionary <int, char> CT = new Dictionary <int, char>();
int cnt = 0;
for (char c = 'a'; c <= 'z'; c++)
{
DT[c] = cnt;
CT[cnt] = c;
cnt++;
}
string[] split = new string[plainText.Length / 3 + (plainText.Length % 3 == 0 ? 0 : 1)];
for (int i = 0; i < split.Length; i++)
{
split[i] = plainText.Substring(i * 3, i * 3 + 3 > plainText.Length ? 1 : 3);
}
string[] splitc = new string[cipherText.Length / 3 + (cipherText.Length % 3 == 0 ? 0 : 1)];
for (int i = 0; i < splitc.Length; i++)
{
splitc[i] = cipherText.ToLower().Substring(i * 3, i * 3 + 3 > cipherText.Length ? 1 : 3);
}
List <string> PermKey = new List <string>();
List <string> ciph = new List <string>();
for (int i = 0; i < split.Length; i++)
{
string perm = "";
string ch = "";
for (int j = i + 2; j < split.Length; j++)
{
perm += split[i] + split[j - 1] + split[j];
ch += splitc[i] + splitc[j - 1] + splitc[j];
PermKey.Add(perm);
ciph.Add(ch);
perm = "";
ch = "";
}
}
List <int> In = new List <int>();
for (int i = 0; i < PermKey.Count; i++)
{
In.Add(r.Inversekey(PermKey[i]));
}
int cnterr = 0;
for (int i = 0; i < In.Count; i++)
{
if (In[i] < 0)
{
cnterr++;
}
}
if (cnterr == In.Count)
{
throw new InvalidAnlysisException();
}
int invMul = 0;
string pl = "";
string ct = "";
for (int i = 0; i < In.Count; i++)
{
if (In[i] > 0)
{
invMul = In[i];
pl = PermKey[i];
ct = ciph[i];
break;
}
}
double[,] keymat = new double[3, 3];
int[,] Ciphermat = new int[3, 3];
int rp = 0;
for (int i = 0; i < 3; i++)
{
int cc = rp;
for (int j = 0; j < 3; j++)
{
keymat[i, j] = DT[pl[cc]];
rp++;
cc++;
}
cc = rp;
}
rp = 0;
for (int i = 0; i < 3; i++)
{
int cc = rp;
for (int j = 0; j < 3; j++)
{
Ciphermat[i, j] = DT[ct[cc]];
rp++;
cc++;
}
cc = rp;
}
/////////////////////////cofactors///////////////////////////////
int[,] matl = new int[3, 3];
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
matl[i, j] = int.Parse(Math.Floor((Math.Pow(-1, i + j) * (int.Parse(Matrix.Determinant(r.CreateSmallerMatrix(keymat, i, j)).ToString())))).ToString());
while (matl[i, j] < 0)
{
matl[i, j] += 26;
}
while (matl[i, j] > 26)
{
matl[i, j] -= 26;
}
}
}
//////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////
int[,] matKeyinverse = new int[3, 3];
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
matKeyinverse[i, j] = matl[j, i];
matKeyinverse[i, j] = (invMul * matKeyinverse[i, j]) % 26;
}
}
//////////////////////////////////inverse///////////////////////////////////
int[,] matRes = new int[3, 3];
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
int sum = 0;
for (int k = 0; k < 3; k++)
{
sum += matKeyinverse[i, k] * Ciphermat[k, j];
}
matRes[i, j] = sum % 26;
}
}
string key = "";
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
key += CT[matRes[j, i]];
}
}
return(key);
}
