anchor.diff:                                     {'in-reply-to', <<"70710@saturn.bell-tel.com, 17320@saturn.bell-tel.com">>}, {'max-forwards', 70},
                                      {'min-expires', <<"213">>}, {'mime-version', <<"1.0">>},
                                      {'organization', <<"Boxes by Bob">>}, {'priority', <<"non-urgent">>},
  -                                   {'proxy-authenticate', <<"Digest realm=\"atlanta.com\"">>},
  +                                   {'proxy-authenticate', <<"Digest realm=\"atlanta.com\"">>}, {'proxy-authorization', <<"Digest username=\"Alice\"">>},
   
   
                                      {'content-length', <<"5">>}, {'via', <<"SIP/2.0/UDP localhost">>},
  
positive.code:                                 {nonce, <<"f84f1cec41e6cbe5aea9c8e88d359">>}, {opaque, <<>>},
                                  {stale, false}, {algorithm, 'MD5'}, {qop, [auth, 'auth-int']},
                                  {param, <<"value">>}]))),
  
       % To
       ?_assertEqual(address(<<"Bob Zert">>, <<"sip:bob@biloxi.com">>, [{'tag', <<"1928301774">>}]),
  
negative.code:     FirstBin = format_auth(First),
      Fun = fun (Val, Acc) -> <<Acc/binary, ?COMMA, ?SP, (format_auth(Val))/binary>> end,
      lists:foldl(Fun, <<SchemeBin/binary, ?SP, FirstBin/binary>>, Rest);
  
  %% 20.28 Proxy-Authorization
  %% http://tools.ietf.org/html/rfc3261#section-20.28
  process(fn, 'proxy-authorization', _Ignore) -> <<"Proxy-Authorization">>;
  process(p, 'proxy-authorization', Bin) ->
      {SchemeBin, Bin2} = sip_binary:parse_token(Bin),
      % parse scheme, the rest is list of paris param=value
      Scheme = sip_binary:binary_to_existing_atom(SchemeBin),
      auth(Scheme, parse_auths(Bin2));
  
  process(f, 'proxy-authorization', Auth) when is_record(Auth, sip_hdr_auth) ->
      SchemeBin = sip_binary:any_to_binary(Auth#sip_hdr_auth.scheme),
      [First | Rest] = Auth#sip_hdr_auth.params,
      FirstBin = format_auth(First),
      Fun = fun (Val, Acc) -> <<Acc/binary, ?COMMA, ?SP, (format_auth(Val))/binary>> end,
      lists:foldl(Fun, <<SchemeBin/binary, ?SP, FirstBin/binary>>, Rest);
  
  
  %% .....
  process(pn, <<"v">>, _Ignore) -> 'via';
  