}// DeriveKey()
internal static void DeriveKey(HMAC keyedHmac, ArraySegment<byte> bufferSegment, ArraySegment<byte> derivedOutput, uint counter = 1)
{
int derivedOutputCount = derivedOutput.Count, derivedOutputOffset = derivedOutput.Offset;
byte[] K_i = null;
HMAC2 keyedHmac2 = keyedHmac as HMAC2;
checked
{
// Calculate each K_i value and copy the leftmost bits to the output buffer as appropriate.
for (var counterStruct = new Utils.IntStruct { UintValue = counter }; derivedOutputCount > 0; ++counterStruct.UintValue)
{
counterStruct.ToBEBytes(bufferSegment.Array, bufferSegment.Offset); // update the counter within the buffer
if (keyedHmac2 == null)
{
K_i = keyedHmac.ComputeHash(bufferSegment.Array, bufferSegment.Offset, bufferSegment.Count);
}
else
{
keyedHmac2.TransformBlock(bufferSegment.Array, bufferSegment.Offset, bufferSegment.Count, null, 0);
keyedHmac2.TransformFinalBlock(bufferSegment.Array, 0, 0);
K_i = keyedHmac2.HashInner;
}
// copy the leftmost bits of K_i into the output buffer
int numBytesToCopy = derivedOutputCount > K_i.Length ? K_i.Length : derivedOutputCount;//Math.Min(derivedOutputCount, K_i.Length);
Utils.BlockCopy(K_i, 0, derivedOutput.Array, derivedOutputOffset, numBytesToCopy);
derivedOutputOffset += numBytesToCopy;
derivedOutputCount -= numBytesToCopy;
}// for
}// checked
if (keyedHmac2 == null && K_i != null) Array.Clear(K_i, 0, K_i.Length); /* clean up needed only when HMAC implementation is not HMAC2 */
}// DeriveKey()
public override byte[] GetBytes(int countBytes)
{
var okm = new byte[countBytes];
if (k_unused > 0)
{
var min = k_unused > countBytes ? countBytes : k_unused;//Math.Min(k_unused, countBytes);
Utils.BlockCopy(k, hashLength - k_unused, okm, 0, min);
countBytes -= min;
k_unused -= min;
}
if (countBytes == 0) return okm;
int n = countBytes / hashLength + 1;
int contextLength = context != null ? context.Length : 0;
byte[] hmac_msg = new byte[hashLength + contextLength + 1];
for (var i = 1; i <= n; ++i)
{
Utils.BlockCopy(k, 0, hmac_msg, 0, k.Length);
if (contextLength > 0)
Utils.BlockCopy(context, 0, hmac_msg, k.Length, contextLength);
hmac_msg[k.Length + contextLength] = checked(++counter);
if (hmac2 != null)
{
hmac2.TransformBlock(hmac_msg, 0, k.Length + contextLength + 1, null, 0);
hmac2.TransformFinalBlock(hmac_msg, 0, 0);
k = hmac2.HashInner;
}
else
k = hmac.ComputeHash(hmac_msg, 0, k.Length + contextLength + 1);
Utils.BlockCopy(k, 0, okm, okm.Length - countBytes, i < n ? hashLength : countBytes);
countBytes -= hashLength;
}
k_unused = -countBytes;
return okm;
}// GetBytes()
byte[] Func()
{
new Utils.IntStruct { UintValue = this.block }.ToBEBytes(inputBuffer);
this.hmac.TransformBlock(inputBuffer: this.salt, inputOffset: 0, inputCount: this.salt.Length, outputBuffer: null, outputOffset: 0);
this.hmac.TransformBlock(inputBuffer: inputBuffer, inputOffset: 0, inputCount: inputBuffer.Length, outputBuffer: null, outputOffset: 0);
this.hmac.TransformFinalBlock(inputBuffer: inputBuffer, inputOffset: 0, inputCount: 0);
byte[] hash = this.hmac.Hash; // creates a copy
this.hmac.Initialize();
byte[] buffer3 = hash;
for (int i = 2; i <= this.iterations; i++)
{
if (hmac2 != null)
{
hmac2.TransformBlock(hash, 0, BlockSize, null, 0);
hmac2.TransformFinalBlock(hash, 0, 0);
hash = hmac2.HashInner;
}
else hash = this.hmac.ComputeHash(hash);
Utils.Xor(dest: buffer3, destOffset: 0, left: hash, leftOffset: 0, byteCount: BlockSize);
}
this.block++;
return buffer3;
}
