Island: Create custom type EncryptionKey32Bit

monkey/monkey_island/cc/server_utils/encryption/key_based_encryptor.py

@@ -15,6 +15,22 @@ logger = logging.getLogger(__name__)
 # Note: password != key
 
 
+class SizeError(Exception):
+    """
+    Raised when an argument is not of the expected size during object creation.
+    """
+
+    pass
+
+
+class EncryptionKey32Bit(bytes):
+    def __init__(self, key: bytes):
+        if len(key) == 32:
+            self.key = key
+        else:
+            raise SizeError("Key size should be 32 bytes.")
+
+
 class KeyBasedEncryptor(IEncryptor):
     def __init__(self, key: bytes):
         """