diff --git a/src/pyfed/storage/__init__.py b/src/pyfed/storage/__init__.py
index 3043df84b346edf6a986171d912ae8350aa3dbba..47de7becdc0edc37b797693d5536ff5480a554e4 100644
--- a/src/pyfed/storage/__init__.py
+++ b/src/pyfed/storage/__init__.py
@@ -7,7 +7,7 @@
 # - Storage provider protocol
 # """
 
-from .base import SQLStorageBackend
+from .base import StorageBackend
 # from .backends.postgresql import PostgreSQLStorage
 # from .backends.mongodb import MongoDBStorageBackend
 # from .backends.redis import RedisStorageBackend
@@ -33,7 +33,7 @@ from .base import SQLStorageBackend
 #     'sqlite': SQLiteStorage
 # }
 
-def get_storage_backend(backend_type: str) -> type[SQLStorageBackend]:
+def get_storage_backend(backend_type: str) -> type[StorageBackend]:
     """Get storage backend class by type."""
     if backend_type not in STORAGE_BACKENDS:
         raise ValueError(f"Unknown storage backend: {backend_type}")
@@ -41,4 +41,4 @@ def get_storage_backend(backend_type: str) -> type[SQLStorageBackend]:
 
 # def register_backend(name: str, backend_class: type[StorageBackend]) -> None:
 #     """Register a new storage backend."""
-#     STORAGE_BACKENDS[name] = backend_class 
\ No newline at end of file
+#     STORAGE_BACKENDS[name] = backend_class 
diff --git a/src/pyfed/utils/exceptions.py b/src/pyfed/utils/exceptions.py
index 9f9958950a65a478275bbdeef02e01e2c25f494b..4b29ce1973435b694e0aac1d4e28d3460b254f1d 100644
--- a/src/pyfed/utils/exceptions.py
+++ b/src/pyfed/utils/exceptions.py
@@ -142,4 +142,8 @@ class IntegrationError(ActivityPubException):
 
 class MiddlewareError(ActivityPubException):
     """Raised when middleware-related errors occur."""
-    pass
\ No newline at end of file
+    pass
+
+class ConfigError(ActivityPubException):
+    """Raised when signature-related errors occur."""
+    pass