private uint[] SecureExpand(byte[] Key)
{
// expanded key size
int keySize = 4 * (m_rndCount + 1);
// hkdf return array
int keyBytes = keySize * 4;
byte[] rawKey = new byte[keyBytes];
HKDF gen = new HKDF(m_kdfExtractor);
// change 1.2: use extract only on an oversized key
if (Key.Length > m_kdfExtractor.BlockSize)
{
// seperate salt and key
m_kdfKeySize = m_kdfExtractor.BlockSize;
byte[] kdfKey = new byte[m_kdfKeySize];
Buffer.BlockCopy(Key, 0, kdfKey, 0, m_kdfKeySize);
int saltSize = Key.Length - m_kdfKeySize;
byte[] kdfSalt = new byte[saltSize];
Buffer.BlockCopy(Key, m_kdfKeySize, kdfSalt, 0, saltSize);
// info can be null
gen.Initialize(kdfKey, kdfSalt, m_kdfInfo);
}
else
{
if (m_kdfInfo.Length != 0)
{
gen.Info = m_kdfInfo;
}
gen.Initialize(Key);
}
gen.Generate(rawKey);
gen.Dispose();
// initialize working key
uint[] expKey = new uint[keySize];
// copy bytes to working key
Buffer.BlockCopy(rawKey, 0, expKey, 0, keyBytes);
return(expKey);
}
