docs: function stamp()
      {
        if(!chat.seq) return fail('chat history overflow, please restart');
        var id = lib.hashname.siphash(mesh.hashname, chat.secret);
        for(var i = 0; i < chat.seq; i++) id = lib.hashname.siphash(id.key,id);
        chat.seq--;
        return lib.base32.encode(id);
      }