public string GetHash(string text)
{
//throw new NotImplementedException();
MatrixOP m = new MatrixOP();
return(m.tohexString(m.ComputeMD5(Encoding.ASCII.GetBytes(text))));
}
public override string Encrypt(string plainText, string key)
{
MatrixOP mp = new MatrixOP();
string[,] S_Box = new string[, ]
{
{ "63", "7c", "77", "7b", "f2", "6b", "6f", "c5", "30", "01", "67", "2b", "fe", "d7", "ab", "76" },
{ "ca", "82", "c9", "7d", "fa", "59", "47", "f0", "ad", "d4", "a2", "af", "9c", "a4", "72", "c0" },
{ "b7", "fd", "93", "26", "36", "3f", "f7", "cc", "34", "a5", "e5", "f1", "71", "d8", "31", "15" },
{ "04", "c7", "23", "c3", "18", "96", "05", "9a", "07", "12", "80", "e2", "eb", "27", "b2", "75" },
{ "09", "83", "2c", "1a", "1b", "6e", "5a", "a0", "52", "3b", "d6", "b3", "29", "e3", "2f", "84" },
{ "53", "d1", "00", "ed", "20", "fc", "b1", "5b", "6a", "cb", "be", "39", "4a", "4c", "58", "cf" },
{ "d0", "ef", "aa", "fb", "43", "4d", "33", "85", "45", "f9", "02", "7f", "50", "3c", "9f", "a8" },
{ "51", "a3", "40", "8f", "92", "9d", "38", "f5", "bc", "b6", "da", "21", "10", "ff", "f3", "d2" },
{ "cd", "0c", "13", "ec", "5f", "97", "44", "17", "c4", "a7", "7e", "3d", "64", "5d", "19", "73" },
{ "60", "81", "4f", "dc", "22", "2a", "90", "88", "46", "ee", "b8", "14", "de", "5e", "0b", "db" },
{ "e0", "32", "3a", "0a", "49", "06", "24", "5c", "c2", "d3", "ac", "62", "91", "95", "e4", "79" },
{ "e7", "c8", "37", "6d", "8d", "d5", "4e", "a9", "6c", "56", "f4", "ea", "65", "7a", "ae", "08" },
{ "ba", "78", "25", "2e", "1c", "a6", "b4", "c6", "e8", "dd", "74", "1f", "4b", "bd", "8b", "8a" },
{ "70", "3e", "b5", "66", "48", "03", "f6", "0e", "61", "35", "57", "b9", "86", "c1", "1d", "9e" },
{ "e1", "f8", "98", "11", "69", "d9", "8e", "94", "9b", "1e", "87", "e9", "ce", "55", "28", "df" },
{ "8c", "a1", "89", "0d", "bf", "e6", "42", "68", "41", "99", "2d", "0f", "b0", "54", "bb", "16" }
};
string[] Bin = new string[] { "0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010"
, "1011", "1100", "1101", "1110", "1111" };
string dec = "0123456789abcdef";
string[,] Rcon = new string[, ] {
{ "01", "02", "04", "08", "10", "20", "40", "80", "1b", "36" },
{ "00", "00", "00", "00", "00", "00", "00", "00", "00", "00" },
{ "00", "00", "00", "00", "00", "00", "00", "00", "00", "00" },
{ "00", "00", "00", "00", "00", "00", "00", "00", "00", "00" }
};
Dictionary <char, string> Cov = new Dictionary <char, string>();
Dictionary <string, char> COVDec = new Dictionary <string, char>();
Dictionary <char, int> subB = new Dictionary <char, int>();
for (int i = 0; i < dec.Length; i++)
{
Cov[dec[i]] = Bin[i];
COVDec[Bin[i]] = dec[i];
subB[dec[i]] = i;
}
string[,] PLaintTextMat = new string[4, 4];
string[,] KeyMat = new string[4, 4];
string[,] AddRoundKey = new string[4, 4];
string[,] SubBytes = new string[4, 4];
string[,] W = new string[4, 4];
string[,] Keycopy = new string[4, 4];
string[,] str = new string[4, 4];
int len1 = (plainText.Length / 2 + (plainText.Length % 2 == 0 ? 0 : 1));
int len2 = (key.Length / 2 + (key.Length % 2 == 0 ? 0 : 1));
List <string> KeyWithoutX = new List <string>();
List <string> plainWithoutX = new List <string>();
///////////////////////////////////////////////////////////
for (int i = 0; i < len1; i++)
{
string ch = plainText.Substring(i * 2, i * 2 + 2 > plainText.Length ? 1 : 2).ToLower();
if (ch == "0x")
{
continue;
}
else
{
plainWithoutX.Add(ch);
}
}
for (int i = 0; i < len2; i++)
{
string ch = key.Substring(i * 2, i * 2 + 2 > key.Length ? 1 : 2).ToLower();
if (ch == "0x")
{
continue;
}
else
{
KeyWithoutX.Add(ch);
}
}
//////////////////////////////////////////////
int cn = 0;
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
PLaintTextMat[j, i] = plainWithoutX[cn];
KeyMat[j, i] = KeyWithoutX[cn];
cn++;
}
}
/////////////////////Add Round Key/////////////////////////////
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
AddRoundKey[i, j] = COVDec[mp.XOR(Cov[PLaintTextMat[i, j][0]], Cov[KeyMat[i, j][0]])].ToString() +
COVDec[mp.XOR(Cov[PLaintTextMat[i, j][1]], Cov[KeyMat[i, j][1]])].ToString();
}
}
///////////////////////////////rounds///////////////////////////////////////
for (int round = 0; round < 9; round++)
{
/////////////////////////////SubBytes////////////////////////////
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
SubBytes[i, j] = S_Box[subB[AddRoundKey[i, j][0]], subB[AddRoundKey[i, j][1]]];
}
}
/////////////////////////////////////shiftRows//////////////////////////////////////////
for (int i = 1; i < 4; i++)
{
int c = i;
while (c > 0)
{
string temp = SubBytes[i, 0];
for (int j = 1; j < 4; j++)
{
SubBytes[i, j - 1] = SubBytes[i, j];
}
SubBytes[i, 3] = temp;
c--;
}
}
/////////////////////////////MixColumn////////////////////////////////////
int[,] decnum = new int[4, 4];
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
int de = int.Parse(SubBytes[i, j], System.Globalization.NumberStyles.HexNumber);
decnum[i, j] = de;
}
}
byte[,] B = new byte[4, 4];
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
B[i, j] = byte.Parse(decnum[i, j].ToString());
}
}
byte[,] BB = mp.MixColumns(B);
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
if (BB[i, j].ToString("X").ToLower().Length < 2)
{
str[i, j] = "0" + BB[i, j].ToString("X").ToLower();
}
else
{
str[i, j] = BB[i, j].ToString("X").ToLower();
}
}
}
///////////////////////////////AddRoundKey/////////////////////////////////
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
Keycopy[i, j] = KeyMat[i, j];
}
}
string tem = KeyMat[0, KeyMat.GetLength(0) - 1];
for (int i = 1; i < 4; i++)
{
KeyMat[i - 1, KeyMat.GetLength(0) - 1] = KeyMat[i, KeyMat.GetLength(0) - 1];
}
KeyMat[KeyMat.GetLength(0) - 1, KeyMat.GetLength(0) - 1] = tem;
for (int i = 0; i < Rcon.GetLength(0); i++)
{
KeyMat[i, KeyMat.GetLength(0) - 1] = S_Box[subB[KeyMat[i, KeyMat.GetLength(0) - 1][0]], subB[KeyMat[i, KeyMat.GetLength(0) - 1][1]]];
}
for (int i = 0; i < 4; i++)
{
string c1 = COVDec[mp.XOR(Cov[KeyMat[i, 0][0]], Cov[KeyMat[i, KeyMat.GetLength(0) - 1][0]])].ToString();
string c2 = COVDec[mp.XOR(Cov[KeyMat[i, 0][1]], Cov[KeyMat[i, KeyMat.GetLength(0) - 1][1]])].ToString();
W[i, 0] = COVDec[mp.XOR(Cov[c1[0]], Cov[Rcon[i, round][0]])].ToString() + COVDec[mp.XOR(Cov[c2[0]], Cov[Rcon[i, round][1]])].ToString();
}
for (int i = 1; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
string ch1 = COVDec[mp.XOR(Cov[Keycopy[j, i][0]], Cov[W[j, i - 1][0]])].ToString();
string ch2 = COVDec[mp.XOR(Cov[Keycopy[j, i][1]], Cov[W[j, i - 1][1]])].ToString();
W[j, i] = ch1 + ch2;
}
}
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
KeyMat[i, j] = W[i, j];
}
}
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
string cs1 = COVDec[mp.XOR(Cov[str[j, i][0]], Cov[KeyMat[j, i][0]])].ToString();
string cs2 = COVDec[mp.XOR(Cov[str[j, i][1]], Cov[KeyMat[j, i][1]])].ToString();
AddRoundKey[j, i] = cs1 + cs2;
}
}
}
/////////////////////////////SubBytes////////////////////////////
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
SubBytes[i, j] = S_Box[subB[AddRoundKey[i, j][0]], subB[AddRoundKey[i, j][1]]];
}
}
/////////////////////////////////////shiftRows//////////////////////////////////////////
for (int i = 1; i < 4; i++)
{
int c = i;
while (c > 0)
{
string temp = SubBytes[i, 0];
for (int j = 1; j < 4; j++)
{
SubBytes[i, j - 1] = SubBytes[i, j];
}
SubBytes[i, 3] = temp;
c--;
}
}
///////////////////////////////////////////////////////////////
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
Keycopy[i, j] = KeyMat[i, j];
}
}
string te = KeyMat[0, KeyMat.GetLength(0) - 1];
for (int i = 1; i < 4; i++)
{
KeyMat[i - 1, KeyMat.GetLength(0) - 1] = KeyMat[i, KeyMat.GetLength(0) - 1];
}
KeyMat[KeyMat.GetLength(0) - 1, KeyMat.GetLength(0) - 1] = te;
for (int i = 0; i < Rcon.GetLength(0); i++)
{
KeyMat[i, KeyMat.GetLength(0) - 1] = S_Box[subB[KeyMat[i, KeyMat.GetLength(0) - 1][0]], subB[KeyMat[i, KeyMat.GetLength(0) - 1][1]]];
}
for (int i = 0; i < 4; i++)
{
string c1 = COVDec[mp.XOR(Cov[KeyMat[i, 0][0]], Cov[KeyMat[i, KeyMat.GetLength(0) - 1][0]])].ToString();
string c2 = COVDec[mp.XOR(Cov[KeyMat[i, 0][1]], Cov[KeyMat[i, KeyMat.GetLength(0) - 1][1]])].ToString();
W[i, 0] = COVDec[mp.XOR(Cov[c1[0]], Cov[Rcon[i, 9][0]])].ToString() + COVDec[mp.XOR(Cov[c2[0]], Cov[Rcon[i, 9][1]])].ToString();
}
for (int i = 1; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
string ch1 = COVDec[mp.XOR(Cov[Keycopy[j, i][0]], Cov[W[j, i - 1][0]])].ToString();
string ch2 = COVDec[mp.XOR(Cov[Keycopy[j, i][1]], Cov[W[j, i - 1][1]])].ToString();
W[j, i] = ch1 + ch2;
}
}
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
KeyMat[i, j] = W[i, j];
}
}
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
string cs1 = COVDec[mp.XOR(Cov[SubBytes[j, i][0]], Cov[KeyMat[j, i][0]])].ToString();
string cs2 = COVDec[mp.XOR(Cov[SubBytes[j, i][1]], Cov[KeyMat[j, i][1]])].ToString();
AddRoundKey[j, i] = cs1 + cs2;
}
}
string CipherText = "";
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
CipherText += AddRoundKey[j, i];
}
}
return("0x" + CipherText.ToUpper());
}
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);
}
public string Decrypt(string cipherText, string key)
{
MatrixOP mp = 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++;
}
int n = key.Length;
if (key.Length % 2 == 0)
{
n = n / 2;
}
else
{
n = (n / 2) - 1;
}
int m = (cipherText.Length / n);
double[,] matKey = new double[n, n];
int[,] matPlain = new int[n, m];
int[,] matRes = new int[n, m];
int rp = 0;
for (int i = 0; i < n; i++)
{
int cc = rp;
for (int j = 0; j < n; j++)
{
matKey[i, j] = DT[key[cc]];
rp++;
cc++;
}
cc = rp;
}
rp = 0;
for (int i = 0; i < m; i++)
{
int cc = rp;
for (int j = 0; j < n; j++)
{
matPlain[j, i] = DT[cipherText.ToLower()[cc]];
rp++;
cc++;
}
cc = rp;
}
int mat = int.Parse(Matrix.Determinant(matKey).ToString()) % 26;
//Console.WriteLine(mat);
while (mat < 0)
{
mat += 26;
}
int x = 0;
for (int b = 0; b < 26; b++)
{
if ((b * mat) % 26 == 1)
{
x = b;
break;
}
}
//Console.WriteLine(x);
int[,] matl = new int[n, n];
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
matl[i, j] = int.Parse(Math.Floor((Math.Pow(-1, i + j) * (int.Parse(Matrix.Determinant(mp.CreateSmallerMatrix(matKey, i, j)).ToString()))) % 26).ToString());
if (matl[i, j] % 26 < 0)
{
matl[i, j] += 26;
}
}
}
/////////////////////////////////
int[,] matKeyinverse = new int[n, n];
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
matKeyinverse[i, j] = matl[j, i];
matKeyinverse[i, j] = (x * matKeyinverse[i, j]) % 26;
}
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
int sum = 0;
for (int k = 0; k < n; k++)
{
sum += matKeyinverse[i, k] * matPlain[k, j];
}
matRes[i, j] = sum % 26;
}
}
string PlaintText = "";
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
PlaintText += CT[matRes[j, i]];
}
}
return(PlaintText.ToLower());
}
public List <int> Decrypt(List <int> cipherText, List <int> key)
{
//throw new NotImplementedException();
MatrixOP mp = new MatrixOP();
int n = key.Count;
if (key.Count % 2 == 0)
{
n = n / 2;
}
else
{
n = (n / 2) - 1;
}
int m = (cipherText.Count / n);
double[,] matKey = new double[n, n];
int[,] matPlain = new int[n, m];
int[,] matRes = new int[n, m];
int rp = 0;
for (int i = 0; i < n; i++)
{
int cc = rp;
for (int j = 0; j < n; j++)
{
matKey[i, j] = key[cc];
rp++;
cc++;
}
cc = rp;
}
rp = 0;
for (int i = 0; i < m; i++)
{
int cc = rp;
for (int j = 0; j < n; j++)
{
matPlain[j, i] = cipherText[cc];
rp++;
cc++;
}
cc = rp;
}
int mat = int.Parse(Matrix.Determinant(matKey).ToString());
//Console.WriteLine(mat);
while (mat < 0)
{
mat += 26;
}
while (mat > 26)
{
mat -= 26;
}
////////////////checking valid///////////////
ExtendedEuclid e = new ExtendedEuclid();
int mulinv = e.GetMultiplicativeInverse(mat, 26);
if (mulinv == -1)
{
throw new InvalidAnlysisException();
}
int[,] matl = new int[n, n];
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
matl[i, j] = int.Parse(Math.Floor((Math.Pow(-1, i + j) * (int.Parse(Matrix.Determinant(mp.CreateSmallerMatrix(matKey, i, j)).ToString()))) % 26).ToString());
if (matl[i, j] % 26 < 0)
{
matl[i, j] += 26;
}
}
}
/////////////////////////////////
int[,] matKeyinverse = new int[n, n];
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
matKeyinverse[i, j] = matl[j, i];
matKeyinverse[i, j] = (mulinv * matKeyinverse[i, j]) % 26;
}
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
int sum = 0;
for (int k = 0; k < n; k++)
{
sum += matKeyinverse[i, k] * matPlain[k, j];
}
matRes[i, j] = sum % 26;
}
}
List <int> PlaintText = new List <int>();
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
PlaintText.Add(matRes[j, i]);
}
}
return(PlaintText);
}
public string Analyse(string plainText, string cipherText)
{
MatrixOP r = new MatrixOP();
//throw new NotImplementedException();
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 / 2 + (plainText.Length % 2 == 0 ? 0 : 1)];
for (int i = 0; i < split.Length; i++)
{
split[i] = plainText.Substring(i * 2, i * 2 + 2 > plainText.Length ? 1 : 2);
}
string[] splitc = new string[cipherText.Length / 2 + (cipherText.Length % 2 == 0 ? 0 : 1)];
for (int i = 0; i < splitc.Length; i++)
{
splitc[i] = cipherText.ToLower().Substring(i * 2, i * 2 + 2 > cipherText.Length ? 1 : 2);
}
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 + 1; j < split.Length; j++)
{
perm += split[i] + split[j];
ch += splitc[i] + splitc[j];
PermKey.Add(perm);
ciph.Add(ch);
perm = "";
ch = "";
}
}
List <int> CalInverse = new List <int>();
for (int i = 0; i < PermKey.Count; i++)
{
CalInverse.Add(r.calculateInverse(PermKey[i]));
}
int cnterr = 0;
for (int i = 0; i < CalInverse.Count; i++)
{
if (CalInverse[i] < 0)
{
cnterr++;
}
}
if (cnterr == CalInverse.Count)
{
throw new InvalidAnlysisException();
}
int invMul = 0;
string pl = "";
string ct = "";
for (int i = 0; i < CalInverse.Count; i++)
{
if (CalInverse[i] > 0)
{
invMul = CalInverse[i];
pl = PermKey[i];
ct = ciph[i];
break;
}
}
////////////////////plaintext/////////////////////
int[,] keymat = new int[2, 2];
int idx = 0;
for (int i = 0; i < 2; i++)
{
int cc = idx;
for (int j = 0; j < 2; j++)
{
keymat[i, j] = DT[pl[idx]];
idx++;
cc++;
}
cc = idx;
}
////////////////////ciphertext//////////////////
int[,] cimat = new int[2, 2];
idx = 0;
for (int i = 0; i < 2; i++)
{
int cc = idx;
for (int j = 0; j < 2; j++)
{
cimat[j, i] = DT[ct[idx]];
idx++;
cc++;
}
cc = idx;
}
///////////////////cofactors//////////////////
int A = keymat[0, 0];
int B = keymat[0, 1];
int C = keymat[1, 0];
int D = keymat[1, 1];
keymat[0, 0] = invMul * D;
keymat[1, 1] = invMul * A;
keymat[1, 0] = invMul * (B * -1);
keymat[0, 1] = invMul * (C * -1);
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 2; j++)
{
while (keymat[i, j] < 0)
{
keymat[i, j] += 26;
}
while (keymat[i, j] > 26)
{
keymat[i, j] -= 26;
}
}
}
int[,] Mulapp = new int[2, 2];
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 2; j++)
{
int sum = 0;
for (int k = 0; k < 2; k++)
{
sum += cimat[i, k] * keymat[k, j];
}
Mulapp[i, j] = sum % 26;
}
}
string key = "";
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 2; j++)
{
key += CT[Mulapp[i, j]];
}
}
return(key);
}