diff --git a/kasa/aestransport.py b/kasa/aestransport.py
index 65b0045..ca74cc6 100644
--- a/kasa/aestransport.py
+++ b/kasa/aestransport.py
@@ -8,7 +8,7 @@ import base64
 import hashlib
 import logging
 import time
-from typing import Dict, Optional, cast
+from typing import Dict, Optional, cast, TYPE_CHECKING
 
 from cryptography.hazmat.primitives import padding, serialization
 from cryptography.hazmat.primitives.asymmetric import padding as asymmetric_padding
@@ -86,6 +86,8 @@ class AesTransport(BaseTransport):
 
         self._login_token = None
 
+        self._key_pair: Optional[KeyPair] = None
+
         _LOGGER.debug("Created AES transport for %s", self._host)
 
     @property
@@ -185,33 +187,35 @@ class AesTransport(BaseTransport):
         self._handle_response_error_code(resp_dict, "Error logging in")
         self._login_token = resp_dict["result"]["token"]
 
+    async def _generate_request_body(self) -> str:
+        """Generate the request body."""
+        self._key_pair = KeyPair.create_key_pair()
+        pub_key = (
+            "-----BEGIN PUBLIC KEY-----\n"
+            + self._key_pair.get_public_key()
+            + "\n-----END PUBLIC KEY-----\n"
+        )
+        handshake_params = {"key": pub_key}
+        _LOGGER.debug(f"Handshake params: {handshake_params}")
+        request_body = {"method": "handshake", "params": handshake_params}
+        _LOGGER.debug(f"Request {request_body}")
+        return json_dumps(request_body)
+
     async def perform_handshake(self):
         """Perform the handshake."""
         _LOGGER.debug("Will perform handshaking...")
         _LOGGER.debug("Generating keypair")
 
+        self._key_pair = None
         self._handshake_done = False
         self._session_expire_at = None
         self._session_cookie = None
 
         url = f"http://{self._host}/app"
-        key_pair = KeyPair.create_key_pair()
-
-        pub_key = (
-            "-----BEGIN PUBLIC KEY-----\n"
-            + key_pair.get_public_key()
-            + "\n-----END PUBLIC KEY-----\n"
-        )
-        handshake_params = {"key": pub_key}
-        _LOGGER.debug(f"Handshake params: {handshake_params}")
-
-        request_body = {"method": "handshake", "params": handshake_params}
-
-        _LOGGER.debug(f"Request {request_body}")
 
         status_code, resp_dict = await self._http_client.post(
             url,
-            json=request_body,
+            data=self._generate_request_body(),
             headers=self.COMMON_HEADERS,
             cookies_dict=self._session_cookie,
         )
@@ -240,8 +244,10 @@ class AesTransport(BaseTransport):
             self._session_cookie = {self.SESSION_COOKIE_NAME: cookie}
 
         self._session_expire_at = time.time() + 86400
+        if TYPE_CHECKING:
+            assert self._key_pair is not None
         self._encryption_session = AesEncyptionSession.create_from_keypair(
-            handshake_key, key_pair
+            handshake_key, self._key_pair
         )
 
         self._handshake_done = True