+ * Checks if a user exists.
+ * @param aUser User to check.
+ * @return True iff user exists.
+ */
+ boolean checkUser(String aUser);
+
+
+ /**
+ * Check if a group exists.
+ * @param aGroup Group.
+ * @return True iff group exists.
+ */
+ boolean checkGroup(String aGroup);
+
+ /**
+ * Checks the password.