private IEnumerable <byte> P_hash(byte[] secret, byte[] seed)
{
var hmac = new HMAC(_digest, secret);
var a = seed;
while (true)
{
hmac.Reset();
hmac.Update(a);
a = hmac.DigestBuffer();
hmac.Reset();
hmac.Update(a);
hmac.Update(seed);
var b = hmac.DigestBuffer();
foreach (var x in b)
{
yield return(x);
}
}
}