anchor.diff:  		S :: binary(),
   		N :: pos_integer(),
   		MK :: binary().
  -%% @doc Pseudo-RANDom Number Function (PRF).
  +%% @doc Pseudo-Random Number Function (PRF).
   %%
   %%      See RFC5448 3.4.
   %% @private
  
positive.code: 	NasId = atom_to_list(node()),
  	[{nas_id, NasId}, {socket, Socket}, {radius_client, RadIP} | Config];
  init_per_testcase(TestCase, Config)
  		when TestCase == identity_radius_trusted ->
  	{ok, RadiusConfig} = application:get_env(ocs, radius),
  	{auth, [{RadIP, _, _} | _]} = lists:keyfind(auth, 1, RadiusConfig),
  	{ok, Socket} = gen_udp:open(0, [{active, false}, inet, {ip, RadIP}, binary]),
  
negative.code: end_per_testcase(TestCase, Config)
  		when TestCase == identity_radius;
  		TestCase == identity_radius_trusted;
  		TestCase == identity_radius_no_client;
  		TestCase == challenge_radius_trusted ->
  	Socket = ?config(socket, Config),
  	RadiusClient = ?config(radius_client, Config),
  	ok = ocs:delete_client(RadiusClient),
  