public override int GenerateBytes(byte[] output, int outOff, int length)
{
if ((output.Length - length) < outOff)
{
throw new DataLengthException("Output Buffer too Small");
}
int outLen = Digest.GetDigestSize();
if (length > outLen)
{
throw new DataLengthException(
"Specified Hash Cannot Produce Sufficient Data for the Specified Operation.");
}
byte[] temp = new byte[Digest.GetDigestSize()];
Digest.BlockUpdate(_shared, 0, _shared.Length);
Digest.DoFinal(temp, 0);
Array.Copy(temp, 0, output, outOff, length);
Digest.Reset();
return(length);
}
/**
* fill len bytes of the output buffer with bytes generated from the
* derivation function.
*
* @throws IllegalArgumentException
* if the size of the request will cause an overflow.
* @throws DataLengthException
* if the out buffer is too small.
*/
public int GenerateBytes(byte[] output, int outOff, int length)
{
if (output.Length - length < outOff)
{
throw new DataLengthException("output buffer too small");
}
long oBytes = length;
int outLen = Digest.GetDigestSize();
//
// this is at odds with the standard implementation, the
// maximum value should be hBits * (2^32 - 1) where hBits
// is the digest output size in bits. We can't have an
// array with a long index at the moment...
//
if (oBytes > (2L << 32) - 1)
{
throw new ArgumentException("Output length too large");
}
int cThreshold = (int)((oBytes + outLen - 1) / outLen);
byte[] digest = new byte[Digest.GetDigestSize()];
// byte[] C = new byte[4];
// Pack.intToBigEndian(counterStart, C, 0);
byte[] c = _counterStart.ToBigEndianByteArray();
Debug.Assert(c.Length == 4, "need to be 4 bytes long");
int counterBase = _counterStart & ~0xFF;
for (int i = 0; i < cThreshold; i++)
{
Digest.BlockUpdate(c, 0, c.Length);
Digest.BlockUpdate(_shared, 0, _shared.Length);
if (_iv != null)
{
Digest.BlockUpdate(_iv, 0, _iv.Length);
}
Digest.DoFinal(digest, 0);
if (length > outLen)
{
Array.Copy(digest, 0, output, outOff, outLen);
outOff += outLen;
length -= outLen;
}
else
{
Array.Copy(digest, 0, output, outOff, length);
}
if (++c[3] == 0)
{
counterBase += 0x100;
// Pack.intToBigEndian(counterBase, C, 0);
c = counterBase.ToBigEndianByteArray();
Debug.Assert(c.Length == 4, "need to be 4 bytes long");
}
}
Digest.Reset();
return((int)oBytes);
}
