diff --git a/src/pyrad3/tools.py b/src/pyrad3/tools.py
index 9af8465..6a444f6 100644
--- a/src/pyrad3/tools.py
+++ b/src/pyrad3/tools.py
@@ -4,6 +4,7 @@
 """Collections of functions to en- and decode RADIUS Attributes"""
 
 import struct
+from functools import partial
 from ipaddress import (
     IPv4Address,
     IPv4Network,
@@ -12,9 +13,10 @@ from ipaddress import (
     ip_address,
     ip_network,
 )
-from typing import Any, Callable, Dict, Union
+from typing import Any, Callable, Dict, Optional, Union
 
 from pyrad3.dictionary import Datatype
+from pyrad3.types import DecodeError
 
 
 def _from_bytes(value: bytes) -> int:
@@ -25,9 +27,7 @@ def encode_string(string: str) -> bytes:
     """Encode a RADIUS value of type string"""
     if len(string) > 253:
         raise ValueError("Can only encode strings of <= 253 characters")
-    if isinstance(string, str):
-        return string.encode("utf-8")
-    return string
+    return string.encode("utf-8")
 
 
 def encode_octets(string: bytes) -> bytes:
@@ -171,8 +171,10 @@ def decode_string(string: bytes) -> Union[str, bytes]:
         return string
 
 
-def decode_octets(string: bytes) -> bytes:
+def decode_octets(string: bytes, length: Optional[int] = None) -> bytes:
     """Decode a RADIUS value of type octets"""
+    if length is not None and len(string) != length:
+        raise DecodeError
     return string
 
 
@@ -234,11 +236,11 @@ ENCODE_MAP: Dict[Datatype, Callable[[Any], bytes]] = {
     # TODO: length check (8)
     Datatype.IFID: encode_octets,
     Datatype.ABINARY: encode_ascend_binary,
-    Datatype.BYTE: lambda value: encode_integer(value, "!B"),
-    Datatype.SHORT: lambda value: encode_integer(value, "!H"),
-    Datatype.SIGNED: lambda value: encode_integer(value, "!i"),
+    Datatype.BYTE: partial(encode_integer, struct_format="!B"),
+    Datatype.SHORT: partial(encode_integer, struct_format="!H"),
+    Datatype.SIGNED: partial(encode_integer, struct_format="!i"),
     Datatype.INTEGER: encode_integer,
-    Datatype.INTEGER64: lambda value: encode_integer(value, "!Q"),
+    Datatype.INTEGER64: partial(encode_integer, struct_format="!Q"),
     Datatype.DATE: encode_date,
 }
 
@@ -260,11 +262,11 @@ DECODE_MAP: Dict[Datatype, Callable[[bytes], Any]] = {
     Datatype.IPV6PREFIX: decode_ipv6_prefix,
     Datatype.COMBOIP: decode_combo_ip,
     # TODO: length check (8)
-    Datatype.IFID: decode_octets,
+    Datatype.IFID: partial(decode_octets, length=8),
     Datatype.ABINARY: decode_ascend_binary,
     Datatype.BYTE: decode_integer,
     Datatype.SHORT: decode_integer,
-    Datatype.SIGNED: lambda num: decode_integer(num, True),
+    Datatype.SIGNED: partial(decode_integer, signed=True),
     Datatype.INTEGER: decode_integer,
     Datatype.INTEGER64: decode_integer,
     Datatype.DATE: decode_date,
diff --git a/src/pyrad3/types.py b/src/pyrad3/types.py
index d3a47ee..d00de5c 100644
--- a/src/pyrad3/types.py
+++ b/src/pyrad3/types.py
@@ -12,6 +12,14 @@ from enum import Enum, IntEnum, auto
 from typing import Dict, List, Tuple, Union
 
 
+class PyradError(Exception):
+    pass
+
+
+class DecodeError(PyradError):
+    pass
+
+
 class Code(IntEnum):
     """Valid RADIUS codes (registered in IANA)"""