Authenticated Chat

Here's a method of authenticating chat with shared secret.

<lsl> //By: Gigs Taggart //Modified by Strife Onizuka //Released under BSD license

string gSetupNotecardName = "setup";

string gPassword; integer gSeed;

key gSetupQueryId; integer gSetupNotecardLine;

//to sign a message we hash message+gSecret+llGetKey() string sign_message(string message) {

   string hash = llMD5String(message + gPassword + (string)llGetKey(), gSeed);
   return message + hash;

}

//to verify a message we do all the same stuff except we get the sender's key integer verify_message(string raw, key sender) {

   string hash = llMD5String(llDeleteSubString(message, -32, -1) + gPassword + (string)sender, gSeed);
   return llGetSubString(message, -32, -1) == hash;

}

readSettingsNotecard() {

  gSetupNotecardLine = 0;
  gSetupQueryId = llGetNotecardLine(gSetupNotecardName, gSetupNotecardLine); 

}

default {

   state_entry()
   {
        readSettingsNotecard();
   }
   dataserver(key queryId, string data)
   {
       if(queryId == gSetupQueryId) 
       {
           if(data != EOF)
           {
               integer split = llSubStringIndex(data, "=");
               if(~split)
               {
                   string setting = llDeleteSubString(data, split, -1);
                   string value   = llDeleteSubString(data, 0,  split);
                   if (setting == "password")
                   {
                       gPassword = value;
                   }
                   else if(setting == "seed")
                   {
                       gSeed = (integer)value;
                   }
               }
               gSetupQueryId = llGetNotecardLine(gSetupNotecardName, ++gSetupNotecardLine); 
           }
           else
           {
               state running;   
           }
       }
   }           
   changed(integer change)
   {
       llResetScript();
   }

}

state running {

   changed(integer change)
   {
       llResetScript();
   }

} </lsl>

Notecard

Name: "setup"

password=secret
seed=0xdeadbeef