I have never heard any rumors nor seen any documentation the the launch codes have ever been changed from 000000000. http://www.cdi.org/blair/permissive-action-links.cfm
The military doesn't seem to think that much of the launch codes, why do you?
If you and a partner have defeated the base security, and gained access to, and secured the launch controls of the nuclear missiles, how much greater of a hurdle is it going to be to get the launch code?
The existence of the launch codes does reduce the chance of an accidental launch, just like paper cutters that require you to press two buttons more than three feet apart reduce the number of limbs accidentally chopped off.
I am sure that their are things that should be kept secret, but that information is smaller than one might first assume.
VMS is like a nightmare about RXS-11M.