public string decrypt(string CipherTxt, int[,] key)
{
string DecRes = "";
CipherTxt = Utilities.removeSpaces(CipherTxt);
int det = Utilities.calculateDeterm(key, key.GetLength(0));
int temp = key.GetLength(0);
det = ((det % 26) + 26) % 26;
/*if (27 % (26 - det) != 0)
* {
* return "";
* }*/
int[,] InversedMat = CalculateCoFactorMat(key);
InversedMat = Utilities.Transpose(InversedMat);
int b = 26 - (27 / (26 - det));
InversedMat = Utilities.elemWiseMult(b, InversedMat);
for (int i = 0; i < CipherTxt.Length; i += temp)
{
int[,] CiConverted = changeStrToVec(CipherTxt.Substring(i, temp));
int[,] PlainText = Utilities.multiply(InversedMat, CiConverted);
for (int j = 0; j < PlainText.GetLength(0); j++)
{
PlainText[j, 0] = ((PlainText[j, 0] % 26) + 26) % 26;
}
DecRes = string.Concat(DecRes, changeVecToStr(PlainText));
}
return(DecRes);
}
public int[,] CalculateCoFactorMat(int[,] key)
{
int n = key.GetLength(0), det;
int [,] temp, res;
res = new int[n, n];
for (int j = 0; j < n; j++)
{
for (int i = 0; i < n; i++)
{
temp = new int[n, n];
int i1 = 0;
for (int ii = 0; ii < n; ii++)
{
if (ii == i)
{
continue;
}
int j1 = 0;
for (int jj = 0; jj < n; jj++)
{
if (jj == j)
{
continue;
}
temp[i1, j1] = key[ii, jj];
j1++;
}
i1++;
}
/* Calculate the determinant */
det = Utilities.calculateDeterm(temp, n - 1);
/* Fill in the elements of the cofactor */
double p = Convert.ToDouble(i + j + 2.0f);
res[i, j] = Convert.ToInt32(Math.Pow(1.0f, p)) * det;
}
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
res[i, j] = ((res[i, j] % 26) + 26) % 26;
}
}
return(res);
}