Add message signing

src/hz.erl

@@ -23,7 +23,7 @@
 %%% @end
 
 -module(hz).
--vsn("0.5.2").
+-vsn("0.6.0").
 -author("Craig Everett <ceverett@tsuriai.jp>").
 -copyright("Craig Everett <ceverett@tsuriai.jp>").
 -license("GPL-3.0-or-later").
@@ -73,6 +73,7 @@
          decode_bytearray_fate/1, decode_bytearray/2,
          spend/5, spend/10,
          sign_tx/2, sign_tx/3,
+         sign_message/2,
          verify_signature/3]).
 
 
@@ -2272,6 +2273,20 @@ spend3(DSenderID,
     hz:post_tx(Encoded).
 
 
+-spec sign_message(Message, SecKey) -> Sig
+    when Message :: binary(),
+         SecKey  :: binary(),
+         Sig     :: binary().
+
+sign_message(Message, SecKey) ->
+    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, SecKey).
+
+
 -spec verify_signature(Sig, Message, PubKey) -> Result
     when Sig     :: binary(),
          Message :: iodata(),