private static int[][] subkey = new int[16][]; // [16][48]
private static int[] Permute(int[] inputBits, int[] keyBits, bool isDecrypt)
{
// Initial permutation step takes input bits and permutes into the
// newBits array
int[] newBits = new int[inputBits.Length];
for (int index = 0; index < inputBits.Length; index++)
{
newBits[index] = inputBits[IP[index] - 1];
}
// 16 rounds will start here
// L and R arrays are created to store the Left and Right halves of the
// subkey respectively
int[] L = new int[32];
int[] R = new int[32];
int i;
// Permuted Choice 1 is done here
for (i = 0; i < 28; i++)
{
C[i] = keyBits[PC1[i] - 1];
}
for (; i < 56; i++)
{
D[i - 28] = keyBits[PC1[i] - 1];
}
// After PC1 the first L and R are ready to be used and hence looping
// can start once L and R are initialized
Array.Copy(newBits, 0, L, 0, 32);
Array.Copy(newBits, 32, R, 0, 32);
Console.Write("\nL0 = ");
DisplayBits(L);
Console.Write("R0 = ");
DisplayBits(R);
for (int n = 0; n < 16; n++)
{
Console.WriteLine("\n-------------");
Console.WriteLine("Round " + (n + 1) + ":");
// newR is the new R half generated by the Fiestel function. If it
// is encrpytion then the KS method is called to generate the
// subkey otherwise the stored subkeys are used in reverse order
// for decryption.
int[] newR = new int[0];
if (isDecrypt)
{
newR = Fiestel(R, subkey[15 - n]);
Console.WriteLine("Round key = ");
DisplayBits(subkey[15 - n]);
}
else
{
newR = Fiestel(R, KS(n, keyBits));
Console.Write("Round key = ");
DisplayBits(subkey[n]);
}
// xor-ing the L and new R gives the new L value. new L is stored
// in R and new R is stored in L, thus exchanging R and L for the
// next round.
int[] newL = XOR(L, newR);
L = R;
R = newL;
Console.Write("L = ");
DisplayBits(L);
Console.Write("R = ");
DisplayBits(R);
}
// R and L has the two halves of the output before applying the
// permutation. This is called the "Preoutput".
int[] output = new int[64];
Array.Copy(R, 0, output, 0, 32);
Array.Copy(L, 0, output, 32, 32);
int[] Output = new int[64];
// Applying FP table to the preoutput, we get the output:
// Encryption => output is ciphertext
// Decryption => output is plaintext
for (i = 0; i < 64; i++)
{
Output[i] = output[FP[i] - 1];
}
// Since the output is stored as an int array of bits, we convert
// it into a hex string:
string hex = string.Empty;
for (i = 0; i < 16; i++)
{
string bin = string.Empty;
for (int j = 0; j < 4; j++)
{
bin += Output[(4 * i) + j];
}
int intValue = Convert.ToInt32(bin, 2); //Integer.parseInt(bin, 2);
hex += HexConverter.IntToHex(intValue); // Integer.toHexString(intValue);
}
if (isDecrypt)
{
Console.Write("Decrypted text: ");
}
else
{
Console.Write("Encrypted text: ");
}
Console.WriteLine(hex.ToUpper());
return(Output);
}