diff --git a/gns3server/utils/encryption.py b/gns3server/utils/encryption.py
index 1f95f497b..38719a60e 100644
--- a/gns3server/utils/encryption.py
+++ b/gns3server/utils/encryption.py
@@ -48,7 +48,7 @@ def init_encryption(secrets_dir: str) -> None:
             os.makedirs(secrets_dir, exist_ok=True)
             with open(encryption_key_path, "w", encoding="utf-8") as f:
                 # Use Fernet's base64-encoded key format
-                f.write(key.decode() if isinstance(key, bytes) else key)
+                f.write(key.decode())
             # Set restrictive permissions (owner read/write only)
             os.chmod(encryption_key_path, 0o600)
         except OSError as e:
@@ -58,7 +58,7 @@ def init_encryption(secrets_dir: str) -> None:
     try:
         with open(encryption_key_path, encoding="utf-8") as f:
             key_content = f.read().strip()
-        key_bytes = key_content.encode() if isinstance(key_content, str) else key_content
+        key_bytes = key_content.encode()
         _fernet = Fernet(key_bytes)
         log.debug("Encryption initialized successfully")
     except OSError as e:
diff --git a/gns3server/utils/images.py b/gns3server/utils/images.py
index c06e22bec..06b4ae9be 100644
--- a/gns3server/utils/images.py
+++ b/gns3server/utils/images.py
@@ -126,7 +126,7 @@ def get_builtin_disks() -> List[str]:
     return builtin_disks
 
 
-async def read_image_info(path: str, expected_image_type: str = None) -> dict:
+async def read_image_info(path: str, expected_image_type: str | None = None) -> dict:
 
     header_magic_len = 7
     try:
@@ -155,7 +155,7 @@ async def read_image_info(path: str, expected_image_type: str = None) -> dict:
     return image_info
 
 
-async def discover_images(image_type: str, skip_image_paths: list = None) -> List[dict]:
+async def discover_images(image_type: str, skip_image_paths: list | None = None) -> List[dict]:
     """
     Scan directories for available images
     """
@@ -378,9 +378,9 @@ async def write_image(
                 f"File '{image_path}' already exists, please choose a different name or remove the existing image"
             )
 
-        checksum = checksum.hexdigest()
+        checksum_hex = checksum.hexdigest()
         image_dir = os.path.dirname(image_path)
-        duplicate_image = await images_repo.get_image_by_checksum(checksum, image_dir)
+        duplicate_image = await images_repo.get_image_by_checksum(checksum_hex, image_dir)
         if duplicate_image:
             raise InvalidImageError(
                 f"Image '{duplicate_image.filename}' with the same checksum already exists in '{image_dir}'"
@@ -396,5 +396,5 @@ async def write_image(
             log.warning(f"Could not remove '{tmp_path}'")
 
     return await images_repo.add_image(
-        image_name, image_type, image_size, image_path, checksum, checksum_algorithm="md5"
+        image_name, image_type, image_size, image_path, checksum_hex, checksum_algorithm="md5"
     )
diff --git a/gns3server/utils/packet_filter_validation.py b/gns3server/utils/packet_filter_validation.py
index cc2634546..1b9481ffd 100644
--- a/gns3server/utils/packet_filter_validation.py
+++ b/gns3server/utils/packet_filter_validation.py
@@ -15,7 +15,7 @@ class FilterValidationError(Exception):
     pass
 
 
-def validate_bpf_syntax(bpf_expression: str) -> Dict[str, Optional[str]]:
+def validate_bpf_syntax(bpf_expression: str) -> Dict[str, Any]:
     """
     Validate BPF filter expression syntax using tcpdump.
 
@@ -78,7 +78,7 @@ def validate_filter_parameters(filter_type: str, values: List[Any]) -> None:
     """
 
     # Define validation rules based on ubridge implementation
-    VALIDATION_RULES = {
+    VALIDATION_RULES: Dict[str, Dict[str, Any]] = {
         "frequency_drop": {
             "params_count": 1,
             "ranges": [(-1, 32767)],  # min, max
@@ -173,11 +173,11 @@ def filter_inactive_filters(filters: Dict[str, List[Any]]) -> Dict[str, List[Any
 
     active_filters = {}
     for filter_type, values in filters.items():
-        if not values or (isinstance(values, list) and len(values) == 0):
+        if not values:
             continue
 
         # Normalize values (strip strings, convert to int)
-        normalized_values = []
+        normalized_values: List[Any] = []
         for value in values:
             if isinstance(value, str):
                 normalized_values.append(value.strip("\n "))
@@ -228,7 +228,7 @@ def validate_all_filters(filters: Dict[str, List[Any]]) -> None:
         return
 
     for filter_type, values in filters.items():
-        if not values or (isinstance(values, list) and len(values) == 0):
+        if not values:
             continue
 
         validate_filter_parameters(filter_type, values)
diff --git a/pyproject.toml b/pyproject.toml
index 4c40679b8..45fc107bb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -372,10 +372,7 @@ module = [
   "gns3server.services.computes",  # 4
   "gns3server.services.templates",  # 18
   "gns3server.utils.asyncio.aiozipstream",  # 8
-  "gns3server.utils.encryption",  # 2
   "gns3server.utils.http_client",  # 4
-  "gns3server.utils.images",  # 4
-  "gns3server.utils.packet_filter_validation",  # 16
   "gns3server.utils.websocket_to_websocket",  # 12
   "gns3server.utils.zipfile_zstd._patcher",  # 1
 ]