anchor.diff:  mac('hmac-sha2-512', Key, SeqNum, Data) ->
   	crypto:hmac(sha512, Key, [<<?UINT32(SeqNum)>>, Data]).
   
  +
  +%%%----------------------------------------------------------------
   %% return N hash bytes (HASH)
   hash(_SSH, _Char, 0) ->
       <<>>;
  
positive.code: 	    yes == yes_no(Ssh, "New host " ++ PeerName ++ " accept")
      end.
  
  known_host_key(#ssh{opts = Opts, key_cb = Mod, peer = Peer} = Ssh, 
  	       Public, Alg) ->
      PeerName = peer_name(Peer),
      case Mod:is_host_key(Public, PeerName, Alg, Opts) of
  	true ->
  	    ok;
  
negative.code: mac_digest_size('AEAD_AES_256_GCM') -> 16;
  mac_digest_size(none) -> 0.
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %%
  %% Diffie-Hellman utils
  