diff --git a/src/clutch.erl b/src/clutch.erl
index 25db1ca..af49889 100644
--- a/src/clutch.erl
+++ b/src/clutch.erl
@@ -55,6 +55,7 @@ start(normal, _Args) ->
                 ok = tell(error, "DANGER! This node is in distributed mode!"),
                 init:stop(1)
         end,
+    ok = application:ensure_started(sasl),
     ok = application:ensure_started(hakuzaru),
     ok = application:ensure_started(zxwidgets),
     gmc_sup:start_link().
diff --git a/src/gmc_con.erl b/src/gmc_con.erl
index 60db7be..41e5fb9 100644
--- a/src/gmc_con.erl
+++ b/src/gmc_con.erl
@@ -15,7 +15,7 @@
          open_wallet/2, close_wallet/0, new_wallet/3, import_wallet/3, drop_wallet/2,
          password/2,
          refresh/0,
-         nonce/1, spend/2, chain/1, grids/1,
+         nonce/1, spend/2, chain/1, grids/1, sign_mess/1,
          make_key/6, recover_key/1, mnemonic/1, rename_key/2, drop_key/1,
          add_node/1, set_sole_node/1]).
 -export([encrypt/2, decrypt/2]).
@@ -147,6 +147,13 @@ grids(String) ->
     gen_server:cast(?MODULE, {grids, String}).
 
 
+-spec sign_mess(Request) -> ok
+    when Request :: map().
+
+sign_mess(Request) ->
+    gen_server:cast(?MODULE, {sign_mess, Request}).
+
+
 -spec make_key(Type, Size, Name, Seed, Encoding, Transform) -> ok
     when Type      :: {eddsa, ed25519},
          Size      :: 256,
@@ -335,6 +342,9 @@ handle_cast({chain, ID}, State) ->
 handle_cast({grids, String}, State) ->
     ok = do_grids(String),
     {noreply, State};
+handle_cast({sign_mess, Request}, State) ->
+    ok = do_sign_mess(Request, State),
+    {noreply, State};
 handle_cast({make_key, Name, Seed, Encoding, Transform}, State) ->
     NewState = do_make_key(Name, Seed, Encoding, Transform, State),
     {noreply, NewState};
@@ -521,9 +531,82 @@ do_grids(String) ->
         Error             -> gmc_gui:trouble(Error)
     end.
 
+do_grids2({{sign, http}, URL}) ->
+    case httpc:request(URL) of
+        {ok, {{_, 200, _}, _, JSON}} -> do_grids_sig(JSON, URL);
+        Error                        -> gmc_gui:trouble(Error)
+    end;
 do_grids2(Instruction) ->
     tell("GRIDS: ~tp", [Instruction]).
 
+do_grids_sig(JSON, URL) ->
+    case zj:decode(JSON) of
+        {ok, GRIDS} -> do_grids_sig2(GRIDS#{"url" => URL});
+        Error       -> gmc_gui:trouble(Error)
+    end.
+
+do_grids_sig2(Request = #{"grids" := 1, "type" := "message"}) ->
+    gmc_gui:grids_mess_sig(Request);
+do_grids_sig2(WTF) ->
+    gmc_gui:trouble({trash, WTF}).
+
+
+do_sign_mess(Request = #{"public_id" := ID, "payload" := Message},
+             #s{wallet = #wallet{keys = Keys}}) ->
+    case lists:keyfind(ID, #key.id, Keys) of
+        #key{pair = #{secret := PrivKey}} ->
+            Sig = base64:encode(sign_message(list_to_binary(Message), PrivKey)),
+            do_sign_mess2(Request#{"signature" => Sig});
+        false ->
+            gmc_gui:trouble({bad_key, ID})
+    end.
+
+do_sign_mess2(Request = #{"url" := URL}) ->
+    ResponseKeys =
+        ["grids",
+         "chain",
+         "network_id",
+         "type",
+         "public_id",
+         "payload",
+         "signature"],
+    Response = zj:encode(maps:with(ResponseKeys, Request)),
+    case httpc:request(post, {URL, [], "application/json", Response}, [], []) of
+        {ok, {{_, 200, _}, _, JSON}} -> log(info, "Signature posted: ~p", [JSON]);
+        Error                        -> gmc_gui:trouble(Error)
+    end.
+
+
+% TODO: Should probably be part of Hakuzaru
+sign_message(Message, PrivKey) ->
+    Prefix = <<"Gajumaru Signed Message:\n">>,
+    {ok, PSize} = vencode(byte_size(Prefix)),
+    {ok, MSize} = vencode(byte_size(Message)),
+    Smashed = iolist_to_binary([PSize, Prefix, MSize, Message]),
+    {ok, Hashed} = eblake2:blake2b(32, Smashed),
+    ecu_eddsa:sign_detached(Hashed, PrivKey).
+
+
+vencode(N) when N < 0 ->
+    {error, {negative_N, N}};
+vencode(N) when N < 16#FD ->
+    {ok, <<N>>};
+vencode(N) when N =< 16#FFFF ->
+    NBytes = eu(N, 2),
+    {ok, <<16#FD, NBytes/binary>>};
+vencode(N) when N =< 16#FFFF_FFFF ->
+    NBytes = eu(N, 4),
+    {ok, <<16#FE, NBytes/binary>>};
+vencode(N) when N < (2 bsl 64) ->
+    NBytes = eu(N, 8),
+    {ok, <<16#FF, NBytes/binary>>}.
+
+eu(N, Size) ->
+    Bytes = binary:encode_unsigned(N, little),
+    NExtraZeros = Size - byte_size(Bytes),
+    ExtraZeros = << <<0>> || _ <- lists:seq(1, NExtraZeros) >>,
+    <<Bytes/binary, ExtraZeros/binary>>.
+
 
 do_spend(KeyID, TX, State = #s{wallet = #wallet{keys = Keys}}) ->
     case lists:keyfind(KeyID, #key.id, Keys) of
diff --git a/src/gmc_gui.erl b/src/gmc_gui.erl
index 7b52e09..f64fa9b 100644
--- a/src/gmc_gui.erl
+++ b/src/gmc_gui.erl
@@ -15,6 +15,7 @@
 -behavior(wx_object).
 -include_lib("wx/include/wx.hrl").
 -export([show/1, wallet/1, chain/2, trouble/1, ask_password/0]).
+-export([grids_mess_sig/1]).
 -export([start_link/1]).
 -export([init/1, terminate/2, code_change/3,
          handle_call/3, handle_cast/2, handle_info/2, handle_event/2]).
@@ -68,6 +69,10 @@ ask_password() ->
     wx_object:cast(?MODULE, password).
 
 
+grids_mess_sig(Request) ->
+    wx_object:cast(?MODULE, {grids_mess_sig, Request}).
+
+
 
 %%% Startup Functions
 
@@ -235,6 +240,9 @@ handle_cast({trouble, Info}, State) ->
 handle_cast(password, State) ->
     ok = do_ask_password(State),
     {noreply, State};
+handle_cast({grids_mess_sig, Request}, State) ->
+    ok = do_grids_mess_sig(Request, State),
+    {noreply, State};
 handle_cast(Unexpected, State) ->
     ok = log(warning, "Unexpected cast: ~tp~n", [Unexpected]),
     {noreply, State}.
@@ -925,6 +933,58 @@ do_ask_password(#s{frame = Frame, prefs = Prefs, j = J}) ->
         end,
     wxDialog:destroy(Dialog).
 
+do_grids_mess_sig(_, #s{accounts = []}) ->
+    ok;
+do_grids_mess_sig(Request = #{"public_id" := false},
+                  State = #s{picker = Picker, accounts = Accounts}) ->
+    case wxListBox:getSelection(Picker) of
+        -1 ->
+            ok;
+        Selected ->
+            #poa{id = ID} = lists:nth(Selected + 1, Accounts),
+            do_grids_mess_sig2(Request#{"public_id" := ID}, State)
+    end.
+
+do_grids_mess_sig2(Request = #{"url" := URL, "public_id" := ID, "payload" := Message},
+                   #s{frame = Frame, j = J}) ->
+    Dialog = wxDialog:new(Frame, ?wxID_ANY, J("Message Signature Request")),
+    Sizer = wxBoxSizer:new(?wxVERTICAL),
+    Instruction =
+        J("The server at the URL below is requesting you sign the following message."),
+    InstTx = wxStaticText:new(Dialog, ?wxID_ANY, Instruction),
+    AcctSz = wxStaticBoxSizer:new(?wxVERTICAL, Dialog, [{label, J("Signature Account")}]),
+    AcctTx = wxStaticText:new(Dialog, ?wxID_ANY, ID),
+    _ = wxStaticBoxSizer:add(AcctSz, AcctTx, zxw:flags(wide)),
+    URL_Label = J("Originating URL"),
+    URL_Sz = wxStaticBoxSizer:new(?wxVERTICAL, Dialog, [{label, URL_Label}]),
+    URL_Tx = wxStaticText:new(Dialog, ?wxID_ANY, URL),
+    _ = wxStaticBoxSizer:add(URL_Sz, URL_Tx, zxw:flags(wide)),
+    MessSz = wxStaticBoxSizer:new(?wxVERTICAL, Dialog, [{label, J("Message")}]),
+    MessTx = wxStaticText:new(Dialog, ?wxID_ANY, Message),
+    _ = wxStaticBoxSizer:add(MessSz, MessTx, zxw:flags(wide)),
+    ButtSz = wxBoxSizer:new(?wxHORIZONTAL),
+    Affirm = wxButton:new(Dialog, ?wxID_OK),
+    Cancel = wxButton:new(Dialog, ?wxID_CANCEL),
+    _ = wxBoxSizer:add(ButtSz, Affirm, zxw:flags(wide)),
+    _ = wxBoxSizer:add(ButtSz, Cancel, zxw:flags(wide)),
+    _ = wxBoxSizer:add(Sizer, InstTx, zxw:flags(wide)),
+    _ = wxBoxSizer:add(Sizer, AcctSz, zxw:flags(wide)),
+    _ = wxBoxSizer:add(Sizer, URL_Sz, zxw:flags(wide)),
+    _ = wxBoxSizer:add(Sizer, MessTx, zxw:flags(wide)),
+    _ = wxBoxSizer:add(Sizer, ButtSz, zxw:flags(base)),
+    ok = wxDialog:setSizer(Dialog, Sizer),
+    ok = wxFrame:setSize(Dialog, {500, 500}),
+    ok = wxBoxSizer:layout(Sizer),
+    ok = wxFrame:center(Dialog),
+    ok =
+        case wxDialog:showModal(Dialog) of
+            ?wxID_OK     -> gmc_con:sign_mess(Request);
+            ?wxID_CANCEL -> ok
+        end,
+    wxDialog:destroy(Dialog);
+do_grids_mess_sig2(BadRequest, _) ->
+    tell("Bad request: ~tp", [BadRequest]).
+    
 
 
 %%% Helpers
diff --git a/src/gmc_v.erl b/src/gmc_v.erl
index 6736057..f8e3309 100644
--- a/src/gmc_v.erl
+++ b/src/gmc_v.erl
@@ -32,15 +32,13 @@ safe_size(Prefs) ->
     Display = wxDisplay:new(),
     GSize = wxDisplay:getGeometry(Display),
     ok = wxDisplay:destroy(Display),
-    Geometry =
-        case maps:find(geometry, Prefs) of
-            {ok, none} ->
-                {X, Y, _, _} = GSize,           
-                {center, {X, Y, 700, 500}};
-            {ok, G} ->
-                {pref, G};
-            error ->
-                {X, Y, _, _} = GSize,           
-                {center, {X, Y, 700, 500}}
-        end,
-    Geometry.
+    case maps:find(geometry, Prefs) of
+        {ok, none} ->
+            {X, Y, _, _} = GSize,           
+            {center, {X, Y, 700, 500}};
+        {ok, G} ->
+            {pref, G};
+        error ->
+            {X, Y, _, _} = GSize,           
+            {center, {X, Y, 700, 500}}
+    end.