Late authentication

I run Debian Wheezy with a simple window manager (Blackbox). If I remember correctly, in Ubuntu some applications like Synaptic and Update Manager ask for sudo password only when/if needed. How do I configure the system so I can launch for instance Update Manager as normal user and only provide sudo password when the system is to be updated?

The window manager is started from ~/.xinitrc with

exec ck-launch-session dbus-launch blackbox

As requested by Graeme the content of directory /usr/share/polkit-1/actions/ is

com.hp.hplip.policy
com.ubuntu.pkexec.synaptic.policy
com.ubuntu.softwareproperties.policy
org.debian.apt.policy
org.freedesktop.color.policy
org.freedesktop.consolekit.policy
org.freedesktop.policykit.policy
org.freedesktop.udisks.policy
org.opensuse.cupspkhelper.mechanism.policy

Below follows the content of the directory /etc/polkit-1/localauthority.conf.d:

$ ls /etc/polkit-1/localauthority.conf.d/
50-localauthority.conf  51-debian-sudo.conf

$ cat /etc/polkit-1/localauthority.conf.d/50-localauthority.conf 
# Configuration file for the PolicyKit Local Authority.
#
# DO NOT EDIT THIS FILE, it will be overwritten on update.
#
# See the pklocalauthority(8) man page for more information
# about configuring the Local Authority.
#

[Configuration]
AdminIdentities=unix-user:0

$ cat /etc/polkit-1/localauthority.conf.d/51-debian-sudo.conf 
[Configuration]
AdminIdentities=unix-group:sudo