public bool TryLookup(byte[] username, out ScramUserCredential user)
 {
     lock (m_users)
     {
         return m_users.TryGetValue(new ReadonlyByteArray(username), out user);
     }
 }
 public void AddUser(string username, string password, int iterations = 4000, int saltSize = 32, HashMethod hashMethod = HashMethod.Sha256)
 {
     var user = new ScramUserCredential(username, password, iterations, saltSize, hashMethod);
     lock (m_users)
     {
         m_users.Add(user.UserBytes, user);
     }
 }