diff --git a/monkey/common/utils/exceptions.py b/monkey/common/utils/exceptions.py
index 50dcb2d6b..dd84380f6 100644
--- a/monkey/common/utils/exceptions.py
+++ b/monkey/common/utils/exceptions.py
@@ -18,6 +18,10 @@ class AlreadyRegisteredError(RegistrationNotNeededError):
     """ Raise to indicate the reason why registration is not required """
 
 
+class UnknownUserError(Exception):
+    """ Raise to indicate that authentication failed """
+
+
 class IncorrectCredentialsError(Exception):
     """ Raise to indicate that authentication failed """
 
diff --git a/monkey/monkey_island/cc/services/authentication/i_user_datastore.py b/monkey/monkey_island/cc/services/authentication/i_user_datastore.py
new file mode 100644
index 000000000..13331963a
--- /dev/null
+++ b/monkey/monkey_island/cc/services/authentication/i_user_datastore.py
@@ -0,0 +1,36 @@
+import abc
+
+from monkey_island.cc.environment.user_creds import UserCreds
+
+
+class IUserDatastore(metaclass=abc.ABCMeta):
+    """
+    Allows user credentials to be stored and retrieved.
+    """
+
+    @abc.abstractmethod
+    def has_registered_users(self) -> bool:
+        """
+        Checks if there are any registered user.
+        :return: True if any users have been registered, False otherwise
+        :rtype: bool
+        """
+
+    @abc.abstractmethod
+    def add_user(self, credentials: UserCreds):
+        """
+        Adds a new user to the datastore.
+        :param UserCreds credentials: New user credentials to persistant storage.
+        :raises InvalidRegistrationCredentialsError: if the credentials are malformed
+        :raises AlreadyRegisteredError: if the user has already been registered
+        """
+
+    @abc.abstractmethod
+    def get_user_credentials(self, username: str) -> UserCreds:
+        """
+        Gets the user matching `username` from storage.
+        :param str username: The username for which credentials will be retrieved
+        :return: User credentials for username
+        :rtype: UserCreds
+        :raises UnknownUserError: if the username does not exist
+        """