// The InvSubBytes Function Substitutes the values in the
// state matrix with values in an InvSbox
static void InvSubBytes(byte[,] state)
{
for (byte col = 0; col < Nb; ++col)
{
state[0, col] = Boxes.getInvSBoxValue(state[0, col]);
state[1, col] = Boxes.getInvSBoxValue(state[1, col]);
state[2, col] = Boxes.getInvSBoxValue(state[2, col]);
state[3, col] = Boxes.getInvSBoxValue(state[3, col]);
}
}//end SubBytes()
//-------------------------------------------------------------------------------------------------------
// This function produces Nb*(Nr+1) round keys. The round keys are used in each round to decrypt the states.
static void KeyExpansion(byte[,] RoundKey, byte[] Key)
{
byte i, j, k;
byte[] tempa = new byte[4]; // Used for the column/row operations
// The first round key is the key itself.
for (i = 0; i < Nk; ++i)
{
RoundKey[0, i] = Key[(i * 4) + 0];
RoundKey[1, i] = Key[(i * 4) + 1];
RoundKey[2, i] = Key[(i * 4) + 2];
RoundKey[3, i] = Key[(i * 4) + 3];
}
//-------------------------------------------
// All other round keys are found from the previous round keys.
for (i = Nk; i < (Nr + 1) * Nb; ++i)//each column !!!!!!!!!
{
{
//k = (byte)((i - 1) * 4);//every 4 column
tempa[0] = RoundKey[0, i - 1];
tempa[1] = RoundKey[1, i - 1];
tempa[2] = RoundKey[2, i - 1];
tempa[3] = RoundKey[3, i - 1];
}
if (i % Nk == 0)
{
// This function shifts the 4 bytes in a word to the left once.
// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
// Function RotWord()
{
byte temp = tempa[0];
tempa[0] = tempa[1];
tempa[1] = tempa[2];
tempa[2] = tempa[3];
tempa[3] = temp;
}
// SubWord() is a function that takes a four-byte input word and
// applies the S-box to each of the four bytes to produce an output word.
// Function Subword()
{
tempa[0] = Boxes.getSBoxValue(tempa[0]);
tempa[1] = Boxes.getSBoxValue(tempa[1]);
tempa[2] = Boxes.getSBoxValue(tempa[2]);
tempa[3] = Boxes.getSBoxValue(tempa[3]);
}
// Function Xor: W(i-nk) ^ W(i-1) ^ Rcon(i/nk-1)
{
tempa[0] = (byte)(RoundKey[0, i - Nk] ^ tempa[0] ^ Rcon[i / Nk]);
tempa[1] = (byte)(RoundKey[1, i - Nk] ^ tempa[1]);
tempa[2] = (byte)(RoundKey[2, i - Nk] ^ tempa[2]);
tempa[3] = (byte)(RoundKey[3, i - Nk] ^ tempa[3]);
}
}
else
{
tempa[0] = (byte)(RoundKey[0, i - 1] ^ RoundKey[0, i - Nk]);
tempa[1] = (byte)(RoundKey[1, i - 1] ^ RoundKey[1, i - Nk]);
tempa[2] = (byte)(RoundKey[2, i - 1] ^ RoundKey[2, i - Nk]);
tempa[3] = (byte)(RoundKey[3, i - 1] ^ RoundKey[3, i - Nk]);
}
//assigment
{
RoundKey[0, i] = tempa[0];
RoundKey[1, i] = tempa[1];
RoundKey[2, i] = tempa[2];
RoundKey[3, i] = tempa[3];
}
}
}
