enables to open encrypted keys with a password

asyncua/client/client.py

@@ -153,11 +153,11 @@ class Client:
         """
         self.user_certificate = await uacrypto.load_certificate(path)
 
-    async def load_private_key(self, path: str):
+    async def load_private_key(self, path, password=None, format=None):
         """
         Load user private key. This is used for authenticating using certificate
         """
-        self.user_private_key = await uacrypto.load_private_key(path)
+        self.user_private_key = await uacrypto.load_private_key(path, password, format)
 
     async def connect_and_get_server_endpoints(self):
         """

asyncua/crypto/uacrypto.py

@@ -27,13 +27,15 @@ def x509_from_der(data):
     return x509.load_der_x509_certificate(data, default_backend())
 
 
-async def load_private_key(path, format=None):
+async def load_private_key(path, password=None, format=None):
     _, ext = os.path.splitext(path)
+    if isinstance(password, str):
+        password.encode('utf-8')
     async with aiofiles.open(path, mode='rb') as f:
         if ext == ".pem" or format == 'pem' or format == 'PEM':
-            return serialization.load_pem_private_key(await f.read(), password=None, backend=default_backend())
+            return serialization.load_pem_private_key(await f.read(), password=password, backend=default_backend())
         else:
-            return serialization.load_der_private_key(await f.read(), password=None, backend=default_backend())
+            return serialization.load_der_private_key(await f.read(), password=password, backend=default_backend())
 
 
 def der_from_x509(certificate):

asyncua/server/server.py

@@ -156,8 +156,8 @@ class Server:
         """
         self.certificate = await uacrypto.load_certificate(path, format)
 
-    async def load_private_key(self, path, format=None):
-        self.iserver.private_key = await uacrypto.load_private_key(path, format)
+    async def load_private_key(self, path, password=None, format=None):
+        self.iserver.private_key = await uacrypto.load_private_key(path, password, format)
 
     def disable_clock(self, val: bool = True):
         """