diff --git a/telethon/network/mtprotoplainsender.py b/telethon/network/mtprotoplainsender.py
index 942c5e02..b53ac24d 100644
--- a/telethon/network/mtprotoplainsender.py
+++ b/telethon/network/mtprotoplainsender.py
@@ -30,7 +30,7 @@ class MTProtoPlainSender:
         body = bytes(request)
         msg_id = self._state._get_new_msg_id()
         await self._connection.send(
-            struct.pack('<QQi', 0, msg_id, len(body)) + body
+            struct.pack('<qqi', 0, msg_id, len(body)) + body
         )
 
         body = await self._connection.recv()
diff --git a/telethon/network/mtprotosender.py b/telethon/network/mtprotosender.py
index 03da7f6b..26c8a52b 100644
--- a/telethon/network/mtprotosender.py
+++ b/telethon/network/mtprotosender.py
@@ -2,11 +2,13 @@ import asyncio
 import collections
 import logging
 
+from . import authenticator
 from .mtprotolayer import MTProtoLayer
+from .mtprotoplainsender import MTProtoPlainSender
 from .requeststate import RequestState
 from .. import utils
 from ..errors import (
-    BadMessageError, TypeNotFoundError, rpc_message_to_error
+    BadMessageError, SecurityError, TypeNotFoundError, rpc_message_to_error
 )
 from ..extensions import BinaryReader
 from ..helpers import _ReadyQueue
@@ -206,18 +208,18 @@ class MTProtoSender:
                                   .format(self._retries))
 
         __log__.debug('Connection success!')
-        # TODO Handle this, maybe an empty MTProtoState that does no encryption
-        """
-        if self.state.auth_key is None:
-            plain = MTProtoPlainSender(self._connection)
+        state = self._connection._state
+        if state.auth_key is None:
+            plain = MTProtoPlainSender(self._connection._connection)
             for retry in range(1, self._retries + 1):
                 try:
                     __log__.debug('New auth_key attempt {}...'.format(retry))
-                    self.state.auth_key, self.state.time_offset =\
+                    state.auth_key, state.time_offset =\
                         await authenticator.do_authentication(plain)
 
+                    # TODO This callback feels out of place
                     if self._auth_key_callback:
-                        self._auth_key_callback(self.state.auth_key)
+                        self._auth_key_callback(state.auth_key)
 
                     break
                 except (SecurityError, AssertionError) as e:
@@ -228,7 +230,6 @@ class MTProtoSender:
                                     .format(self._retries))
                 await self._disconnect(error=e)
                 raise e
-        """
 
         __log__.debug('Starting send loop')
         self._send_loop_handle = self._loop.create_task(self._send_loop())
diff --git a/telethon/network/mtprotostate.py b/telethon/network/mtprotostate.py
index ebf2cb21..761b869f 100644
--- a/telethon/network/mtprotostate.py
+++ b/telethon/network/mtprotostate.py
@@ -28,6 +28,14 @@ class MTProtoState:
     for all these is not a good idea as each need their own authkey, and
     the concept of "copying" sessions with the unnecessary entities or
     updates state for these connections doesn't make sense.
+
+    While it would be possible to have a `MTProtoPlainState` that does no
+    encryption so that it was usable through the `MTProtoLayer` and thus
+    avoid the need for a `MTProtoPlainSender`, the `MTProtoLayer` is more
+    focused to efficiency and this state is also more advanced (since it
+    supports gzipping and invoking after other message IDs). There are too
+    many methods that would be needed to make it convenient to use for the
+    authentication process, at which point the `MTProtoPlainSender` is better.
     """
     def __init__(self, auth_key):
         # Session IDs can be random on every connection