private void BlockMix(ArraySegment <byte> B, byte[] Y)
{
ArraySegment <byte> .Copy(B, (2 * BlockSize - 1) * 64, BlockX, 0, 64);
for (int i = 0; i < 2 * BlockSize; ++i)
{
for (int j = 0; j < 64; ++j)
{
BlockX[j] ^= B[i * 64 + j];
}
Salsa.ComputeHash(BlockX, BlockX);
Array.Copy(BlockX, 0, Y, i * 64, 64);
}
for (int i = 0; i < BlockSize; ++i)
{
ArraySegment <byte> .Copy(Y, (i * 2) * 64, B, i * 64, 64);
}
for (int i = 0; i < BlockSize; ++i)
{
ArraySegment <byte> .Copy(Y, (i * 2 + 1) * 64, B, (i + BlockSize) * 64, 64);
}
}
public override byte[] DeriveBytes(int count)
{
if (count > 64)
{
throw new ArgumentException("Salsa20 can only derive up to 64 bytes.", "count");
}
byte[] hash;
var block = new byte[64];
if (Key.Length == 16)
{
block[0] = 101;
block[1] = 120;
block[2] = 112;
block[3] = 97;
Array.Copy(Key, 0, block, 4, 16);
block[20] = 110;
block[21] = 100;
block[22] = 32;
block[23] = 49;
Array.Copy(Nonce, 0, block, 24, 16);
block[40] = 54;
block[41] = 45;
block[42] = 98;
block[43] = 121;
Array.Copy(Key, 0, block, 44, 16);
block[60] = 116;
block[61] = 101;
block[62] = 32;
block[63] = 107;
hash = Salsa.ComputeHash(block);
}
else
{
block[0] = 101;
block[1] = 120;
block[2] = 112;
block[3] = 97;
Array.Copy(Key, 0, block, 4, 16);
block[20] = 110;
block[21] = 100;
block[22] = 32;
block[23] = 51;
Array.Copy(Nonce, 0, block, 24, 16);
block[40] = 50;
block[41] = 45;
block[42] = 98;
block[43] = 121;
Array.Copy(Key, 16, block, 44, 16);
block[60] = 116;
block[61] = 101;
block[62] = 32;
block[63] = 107;
hash = Salsa.ComputeHash(block);
}
var result = new byte[count];
Array.Copy(hash, result, count);
return(result);
}