diff --git a/app/helper.py b/app/helper.py
index 6684de6..b416ab3 100644
--- a/app/helper.py
+++ b/app/helper.py
@@ -1,6 +1,5 @@
-from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKeyWithSerialization
-from cryptography.hazmat.primitives.serialization import load_pem_private_key, Encoding, PrivateFormat, PublicFormat, \
-    NoEncryption
+from Crypto.PublicKey import RSA
+from Crypto.PublicKey.RSA import RsaKey
 
 
 def load_file(filename) -> bytes:
@@ -9,20 +8,13 @@ def load_file(filename) -> bytes:
     return content
 
 
-def load_key(filename) -> RSAPrivateKeyWithSerialization:
-    return load_pem_private_key(data=load_file(filename), password=None)
+def load_key(filename) -> RsaKey:
+    return RSA.import_key(extern_key=load_file(filename), passphrase=None)
 
 
-def private_bytes(rsa: RSAPrivateKeyWithSerialization) -> bytes:
-    return rsa.private_bytes(
-        encoding=Encoding.PEM,
-        format=PrivateFormat.TraditionalOpenSSL,
-        encryption_algorithm=NoEncryption()
-    )
+def private_bytes(rsa: RsaKey) -> bytes:
+    return rsa.export_key(format='PEM', passphrase=None, protection=None)
 
 
-def public_key(rsa: RSAPrivateKeyWithSerialization) -> bytes:
-    return rsa.public_key().public_bytes(
-        encoding=Encoding.PEM,
-        format=PublicFormat.SubjectPublicKeyInfo
-    )
+def public_key(rsa: RsaKey) -> bytes:
+    return rsa.public_key().export_key(format='PEM')
diff --git a/requirements.txt b/requirements.txt
index 5cc4f28..878b29d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
 fastapi==0.88.0
 uvicorn[standard]==0.20.0
 python-jose==3.3.0
-cryptography==38.0.4
\ No newline at end of file
+pycryptodome==3.16.0