diff --git a/libp2p/crypto/authenticated_encryption.py b/libp2p/crypto/authenticated_encryption.py
index 733d4b5..6900f1f 100644
--- a/libp2p/crypto/authenticated_encryption.py
+++ b/libp2p/crypto/authenticated_encryption.py
@@ -3,6 +3,7 @@ import hmac
 from typing import Tuple
 
 from Crypto.Cipher import AES
+import Crypto.Util.Counter as Counter
 
 
 class InvalidMACException(Exception):
@@ -23,8 +24,14 @@ class MacAndCipher:
         self.authenticator = hmac.new(
             parameters.mac_key, digestmod=parameters.hash_type
         )
+        iv_bit_size = 8 * len(parameters.iv)
         cipher = AES.new(
-            parameters.cipher_key, AES.MODE_CTR, initial_value=parameters.iv
+            parameters.cipher_key,
+            AES.MODE_CTR,
+            counter=Counter.new(
+                iv_bit_size,
+                initial_value=int.from_bytes(parameters.iv, byteorder="big"),
+            ),
         )
         self.cipher = cipher
 
@@ -70,14 +77,16 @@ def initialize_pair(
     hmac_key_size = 20
     seed = "key expansion".encode()
 
-    result = bytearray(2 * (iv_size + cipher_key_size + hmac_key_size))
+    params_size = iv_size + cipher_key_size + hmac_key_size
+    result = bytearray(2 * params_size)
 
     authenticator = hmac.new(secret, digestmod=hash_type)
     authenticator.update(seed)
     tag = authenticator.digest()
 
     i = 0
-    while i < len(result):
+    len_result = 2 * params_size
+    while i < len_result:
         authenticator = hmac.new(secret, digestmod=hash_type)
 
         authenticator.update(tag)
@@ -87,10 +96,10 @@ def initialize_pair(
 
         remaining_bytes = len(another_tag)
 
-        if i + remaining_bytes > len(result):
-            remaining_bytes = len(result) - i
+        if i + remaining_bytes > len_result:
+            remaining_bytes = len_result - i
 
-        result[i : i + remaining_bytes] = another_tag
+        result[i : i + remaining_bytes] = another_tag[0:remaining_bytes]
 
         i += remaining_bytes
 
@@ -98,23 +107,22 @@ def initialize_pair(
         authenticator.update(tag)
         tag = authenticator.digest()
 
-    half = int(len(result) / 2)
-    first_half = result[:half]
-    second_half = result[half:]
+    first_half = result[:params_size]
+    second_half = result[params_size:]
 
     return (
         EncryptionParameters(
             cipher_type,
             hash_type,
             first_half[0:iv_size],
-            first_half[iv_size : iv_size + cipher_key_size],
             first_half[iv_size + cipher_key_size :],
+            first_half[iv_size : iv_size + cipher_key_size],
         ),
         EncryptionParameters(
             cipher_type,
             hash_type,
             second_half[0:iv_size],
-            second_half[iv_size : iv_size + cipher_key_size],
             second_half[iv_size + cipher_key_size :],
+            second_half[iv_size : iv_size + cipher_key_size],
         ),
     )
diff --git a/libp2p/crypto/key_exchange.py b/libp2p/crypto/key_exchange.py
index 5da467f..70e7944 100644
--- a/libp2p/crypto/key_exchange.py
+++ b/libp2p/crypto/key_exchange.py
@@ -23,6 +23,6 @@ def create_ephemeral_key_pair(curve_type: str) -> Tuple[PublicKey, SharedKeyGene
         private_key = cast(ECCPrivateKey, key_pair.private_key)
         secret_point = curve_point * private_key.impl.d
         byte_size = secret_point.size_in_bytes()
-        return secret_point.x.to_bytes(byte_size, byteorder="big")
+        return secret_point.x.to_bytes(byte_size)
 
     return key_pair.public_key, _key_exchange
diff --git a/libp2p/security/secio/transport.py b/libp2p/security/secio/transport.py
index e1d4530..272639e 100644
--- a/libp2p/security/secio/transport.py
+++ b/libp2p/security/secio/transport.py
@@ -85,7 +85,7 @@ class SecureSession(BaseSession):
         tag = self.local_encrypter.authenticate(encrypted_data)
         msg = encode_message(encrypted_data + tag)
         # TODO clean up how we write messages
-        self.conn.writer.write(msg)
+        await self.conn.writer.write(msg)
         await self.conn.writer.drain()
 
 
@@ -104,18 +104,17 @@ class Proposal:
 
     def serialize(self) -> bytes:
         protobuf = Propose(
-            self.nonce,
-            self.public_key.serialize(),
-            self.exchanges,
-            self.ciphers,
-            self.hashes,
+            rand=self.nonce,
+            public_key=self.public_key.serialize(),
+            exchanges=self.exchanges,
+            ciphers=self.ciphers,
+            hashes=self.hashes,
         )
         return protobuf.SerializeToString()
 
     @classmethod
     def deserialize(cls, protobuf_bytes: bytes) -> "Proposal":
-        protobuf = Propose()
-        protobuf.ParseFromString(protobuf_bytes)
+        protobuf = Propose.FromString(protobuf_bytes)
 
         nonce = protobuf.rand
         public_key_protobuf_bytes = protobuf.public_key
@@ -163,15 +162,14 @@ class SessionParameters:
 async def _response_to_msg(conn: IRawConnection, msg: bytes) -> bytes:
     # TODO clean up ``IRawConnection`` so that we don't have to break
     # the abstraction
-    conn.writer.write(encode_message(msg))
+    await conn.writer.write(encode_message(msg))
     await conn.writer.drain()
 
     return await read_next_message(conn.reader)
 
 
 def _mk_multihash_sha256(data: bytes) -> bytes:
-    digest = hashlib.sha256(data).digest()
-    return multihash.encode(digest, "sha2-256")
+    return multihash.digest(data, "sha2-256")
 
 
 def _mk_score(public_key: PublicKey, nonce: bytes) -> bytes: