private byte[] ProcessDecrypt(byte[] byteInput, string password)
{
if (password.Length != blockSize)
{
throw new Exception("Password is not 128bit long");
}
var result = new List <byte>();
//We will divide the byteInput into Block of 16 chars
var blockIteration = (int)Math.Ceiling((byteInput.Length * 1.0) / blockSize);
var currentByteBlock = new byte[4, 4];
var cbcBlock = new byte[4, 4];
BlockFill(cbcBlock, 0);
var substitute = new Substitution();
var addKey = new AddKey(substitute, password);
var mixColumn = new MixColumns();
var shiftRow = new ShiftRow();
for (var blockCount = 0; blockCount < blockIteration; blockCount++)
{
var blockStart = blockCount * blockSize;
var cipherCBC = new byte[4, 4];
//COnvert to a blockArray of 4x4
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
currentByteBlock[j, i] = byteInput[blockStart + i * 4 + j];
cipherCBC[j, i] = currentByteBlock[j, i];
}
}
LogEngine.LogBytes(currentByteBlock, "Current Block");
addKey.AddRoundKey(Nr, currentByteBlock);
shiftRow.InvByteShift(currentByteBlock);
substitute.InvByteSub(currentByteBlock);
for (int rnd = Nr - 1; rnd > 0; rnd--)
{
addKey.AddRoundKey(rnd, currentByteBlock);
mixColumn.InvApplyColumn(currentByteBlock);
shiftRow.InvByteShift(currentByteBlock);
substitute.InvByteSub(currentByteBlock);
}
addKey.AddRoundKey(0, currentByteBlock);
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 4; j++)
{
result.Add((byte)(cbcBlock[j, i] ^ currentByteBlock[j, i]));
}
}
//Copy this stage Cypher as next stage CBC
BlockCopy(cipherCBC, cbcBlock);
}
addKey.Dispose();
return(result.ToArray());
}