Key storage file ownership

The last user to access the key storage file owns it, due to the internals of the key storage functions.

The file is recreated after being compressed, and due to the file creation the owner is changed.

Having the set-group-id bit ( g+s ) on in the directory permission causes the file to be created with the group owner the same as the directory group owner. The group read/write permissions on the file then allow the other members of the group continued access to the file.