diff --git a/app/main.py b/app/main.py
index a30d205..29e5c95 100644
--- a/app/main.py
+++ b/app/main.py
@@ -4,10 +4,9 @@ from calendar import timegm
 from contextlib import asynccontextmanager
 from datetime import datetime, timedelta, UTC
 from hashlib import sha256
-from json import loads as json_loads
+from json import loads as json_loads, dumps as json_dumps
 from os import getenv as env
 from os.path import join, dirname, isfile
-from random import randbytes
 from uuid import uuid4
 
 from dateutil.relativedelta import relativedelta
@@ -728,7 +727,8 @@ async def leasing_v1_lessor(request: Request):
 
     logger.debug(response)
 
-    signature = f'b\'{randbytes(256).hex()}\''
+    signature = INSTANCE_KEY_RSA.generate_signature(json_dumps(response).encode('utf-8'))
+    signature = f'b\'{signature.hex()}\''
     return JSONr(response, headers={'access-control-expose-headers': 'X-NLS-Signature', 'X-NLS-Signature': signature})
 
 
@@ -780,7 +780,8 @@ async def leasing_v1_lease_renew(request: Request, lease_ref: str):
 
     Lease.renew(db, entity, expires, cur_time)
 
-    signature = f'b\'{randbytes(256).hex()}\''
+    signature = INSTANCE_KEY_RSA.generate_signature(json_dumps(response).encode('utf-8'))
+    signature = f'b\'{signature.hex()}\''
     return JSONr(response, headers={'access-control-expose-headers': 'X-NLS-Signature', 'X-NLS-Signature': signature})
 
 
diff --git a/app/util.py b/app/util.py
index a8288de..c5b0187 100644
--- a/app/util.py
+++ b/app/util.py
@@ -1,7 +1,9 @@
 import logging
-
+from json import loads as json_loads
 from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric.padding import PKCS1v15
 from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey, RSAPublicKey, generate_private_key
+from cryptography.hazmat.primitives.hashes import SHA256
 from cryptography.hazmat.primitives.serialization import load_pem_private_key, load_pem_public_key
 from cryptography.x509 import load_pem_x509_certificate, Certificate
 
@@ -40,6 +42,9 @@ class PrivateKey:
         )
         return PublicKey(data=data)
 
+    def generate_signature(self, data: bytes) -> bytes:
+        return self.__key.sign(data, PKCS1v15(), SHA256())
+
     @staticmethod
     def generate(public_exponent: int = 65537, key_size: int = 2048) -> "PrivateKey":
         log = logging.getLogger(__name__)