Update GRIDS

GRIDS.md

@@ -214,17 +214,15 @@ The response to the initial GET request takes the form of a JSON object with thi
     use (and then populate this field).
   - If an ID is specified, then the client should select that account or fail if it is not available.
 - The `"payload"` is the data to be signed. In the case of a
-  `"tx"` request (a contract call, for example), this data
-  will be transaction data encoded according to the Gajumaru
-  protocol's rules. Any Gajumaru signature routine will
-  understand how to interpret and handle this data. In the
-  case of a `"message"` request, this will typically be a
-  simple string in plain text that the client interprets as a
-  binary string, prepends the binary string (Erlang binary notation)
-  `<<"Gajumaru Signed Message:\n">>`, and then signs.
-  Prefixing message request payloads with this string prevents
-  attackers from disguising transaction signature requests as
-  text message signatures.
+  `"tx"` request (a contract call, for example), this data will be transaction data encoded according to the Gajumaru
+  protocol's rules. Any Gajumaru signature routine will understand how to interpret and handle this data.
+  Each signature context has its own requirements:
+  - `"tx"` signatures must be handled according to the Gajumaru protocol rules for transaction signatures.
+  - `"message"`signatures are for simple UTF8 strings in plain text that the client interprets as a binary string.
+    The binary string `<<"Gajumaru Signed Message:\n">>` is prepended to the message text before the signature is performed.
+    Prefixing message request payloads with this string prevents attackers from disguising transaction signature requests as text message signatures.
+  - `"binary"` signatures are for data encoded in base64.
+    The contents are first decoded from base64, then the binary prefix `<<"Gajumaru Signed Binary:">>` is prepended to the binary data before the signature is performed.
 
 ### Signed Data Messages (subsequent POST)