@@ -72,7 +72,7 @@ class SecurityGenerateAuthorization(rq.ReplyRequest):
                          rq.LengthOf('auth_data', 2),
                          rq.Card32('value_mask'),
                          rq.String8('auth_proto'),
-                         rq.Bytes('auth_data'),
+                         rq.Binary('auth_data'),
                          rq.List('values', rq.Card32Obj)
                          )
     _reply = rq.Struct(rq.ReplyCode(),
@@ -82,11 +82,11 @@ class SecurityGenerateAuthorization(rq.ReplyRequest):
                        AUTHID('authid'),
                        rq.LengthOf('auth_data_return', 2),
                        rq.Pad(18),
-                       rq.Bytes('auth_data_return')
+                       rq.Binary('auth_data_return')
                        )
 
 
-def generate_authorization(self, auth_proto, auth_data='', timeout=None,
+def generate_authorization(self, auth_proto, auth_data=b'', timeout=None,
                            trust_level=None, group=None, event_mask=None):
     value_mask = 0
     values = []
 
@@ -29,7 +29,7 @@ class AnyEvent(rq.Event):
     _fields = rq.Struct( rq.Card8('type'),
                          rq.Card8('detail'),
                          rq.Card16('sequence_number'),
-                         rq.FixedString('data', 28),
+                         rq.FixedBinary('data', 28),
                          )
 
 class KeyButtonPointer(rq.Event):
 
@@ -364,26 +364,23 @@ def __init__(self, name):
                                     X.SouthEastGravity))
 
 
-class FixedString(ValueField):
+class FixedBinary(ValueField):
     structvalues = 1
 
     def __init__(self, name, size):
         ValueField.__init__(self, name)
         self.structcode = '{0}s'.format(size)
 
 
-class Bytes(ValueField):
+class Binary(ValueField):
     structcode = None
 
     def __init__(self, name, pad = 1):
         ValueField.__init__(self, name)
         self.pad = pad
 
     def pack_value(self, val):
-        if isinstance(val, bytes):
-            val_bytes = val
-        else:
-            val_bytes = val.encode()
+        val_bytes = val
         slen = len(val_bytes)
 
         if self.pad:
@@ -400,9 +397,7 @@ def parse_binary_value(self, data, display, length, format):
         else:
             slen = length
 
-        data_bytes = data[:length]
-
-        return data_bytes, data[slen:]
+        return data[:length], data[slen:]
 
 
 class String8(ValueField):
Original file line number	Diff line number	Diff line change
`@@ -29,7 +29,7 @@ class AnyEvent(rq.Event):`
`29`	`29`	`_fields = rq.Struct( rq.Card8('type'),`
`30`	`30`	`rq.Card8('detail'),`
`31`	`31`	`rq.Card16('sequence_number'),`
`32`		`- rq.FixedString('data', 28),`
	`32`	`+ rq.FixedBinary('data', 28),`
`33`	`33`	`)`
`34`	`34`
`35`	`35`	`class KeyButtonPointer(rq.Event):`