/// <summary>
/// Устанавливает первичные настройки для блоков текста и ключа
/// </summary>
/// <param name="blockSize"></param>
/// <param name="keySize"></param>
/// <param name="key"></param>
public void SetSettings(BlockSize blockSize, KeySize keySize, byte[] key)
{
var keyLengthInBytes = RijndaelSizesConverter.KeySizeToInt(keySize) / 8;
if (key.Length != keyLengthInBytes)
{
throw new Exception("Неверная длина ключа");
}
_blockSize = blockSize;
_keySize = keySize;
_key = key;
GenerateKeyExpansion();
}
/// <summary>
/// Генерирует набор ключей для шифрования и дешифрования
/// </summary>
private void GenerateKeyExpansion()
{
var blockSize = _blockSize;
var keySize = _keySize;
var key = _key;
var blockSizeBits = RijndaelSizesConverter.BlockSizeToInt(blockSize);
var nb = blockSizeBits / 32;
var nr = GetAmountRounds(blockSize, keySize); // amount rounds
var nk = RijndaelSizesConverter.KeySizeToInt(keySize) / 32; // amount of columns
switch (blockSizeBits > key.Length * 8 ? blockSizeBits : key.Length * 8)
{
case 128:
nr = 10;
break;
case 192:
nr = 12;
break;
case 256:
nr = 14;
break;
default:
throw new Exception("InvalidKeySize");
}
_encryptKeyExpansion = new int[nb * (nr + 1)];
_decryptKeyExpansion = new int[nb * (nr + 1)];
int iTemp;
var index = 0;
for (var i = 0; i < nk; ++i)
{
int i0 = key[index++];
int i1 = key[index++];
int i2 = key[index++];
int i3 = key[index++];
_encryptKeyExpansion[i] = i3 << 24 | i2 << 16 | i1 << 8 | i0;
}
if (nk <= 6)
{
for (var i = nk; i < nb * (nr + 1); ++i)
{
iTemp = _encryptKeyExpansion[i - 1];
if (i % nk == 0)
{
iTemp = SubWord(Rot3(iTemp));
iTemp ^= RijndaelTables.Rcon[(i / nk) - 1];
}
_encryptKeyExpansion[i] = _encryptKeyExpansion[i - nk] ^ iTemp;
}
}
else
{
for (var i = nk; i < nb * (nr + 1); ++i)
{
iTemp = _encryptKeyExpansion[i - 1];
if (i % nk == 0)
{
iTemp = SubWord(Rot3(iTemp));
iTemp ^= RijndaelTables.Rcon[(i / nk) - 1];
}
else if (i % nk == 4)
{
iTemp = SubWord(iTemp);
}
_encryptKeyExpansion[i] = _encryptKeyExpansion[i - nk] ^ iTemp;
}
}
for (var i = 0; i < nb; ++i)
{
_decryptKeyExpansion[i] = _encryptKeyExpansion[i];
_decryptKeyExpansion[nb * nr + i] = _encryptKeyExpansion[nb * nr + i];
}
for (var i = nb; i < nb * nr; ++i)
{
var tmpKey = _encryptKeyExpansion[i];
var mul02 = MulX(tmpKey);
var mul04 = MulX(mul02);
var mul08 = MulX(mul04);
var mul09 = tmpKey ^ mul08;
_decryptKeyExpansion[i] = mul02 ^ mul04 ^ mul08 ^ Rot3(mul02 ^ mul09) ^ Rot2(mul04 ^ mul09) ^ Rot1(mul09);
}
for (var i = 0; i < nr + 1; i++)
{
for (var k = 0; k < nb; k++)
{
_decryptKeyExpansion[i * nb + k] = _encryptKeyExpansion[(nr - i) * nb + k];
}
}
}
