public Rfc2898DeriveBytes(string password, int saltSize, int iterations, HashAlgorithmName hashAlgorithm)
{
if (saltSize < 0)
{
throw new ArgumentOutOfRangeException(nameof(saltSize), ArgumentOutOfRange_NeedNonNegNum);
}
if (saltSize < MinimumSaltSize)
{
throw new ArgumentException(Cryptography_PasswordDerivedBytes_FewBytesSalt, nameof(saltSize));
}
if (iterations <= 0)
{
throw new ArgumentOutOfRangeException(nameof(iterations), ArgumentOutOfRange_NeedPosNum);
}
_salt = CryptographyHelpers.GenerateRandom(saltSize);
_iterations = (uint)iterations;
_password = Encoding.UTF8.GetBytes(password);
HashAlgorithm = hashAlgorithm;
_hmac = OpenHmac();
// _blockSize is in bytes, HashSize is in bits.
_blockSize = _hmac.HashSize >> 3;
Initialize();
}
// This function is defined as follows:
// Func (S, i) = HMAC(S || i) | HMAC2(S || i) | ... | HMAC(iterations) (S || i)
// where i is the block number.
private byte[] Func()
{
byte[] temp = new byte[_salt.Length + sizeof(uint)];
Buffer.BlockCopy(_salt, 0, temp, 0, _salt.Length);
CryptographyHelpers.WriteInt(_block, temp, _salt.Length);
temp = _hmac.ComputeHash(temp);
byte[] ret = temp;
for (int i = 2; i <= _iterations; i++)
{
temp = _hmac.ComputeHash(temp);
for (int j = 0; j < _blockSize; j++)
{
ret[j] ^= temp[j];
}
}
// increment the block count.
_block++;
return(ret);
}