According to this story:
http://www.cdi.org/blair/permissive-action-links.cfm
...from the 1960's through 1977, the high-security 8-digit launch code for minuteman ICBM's was:
0 0 0 0 0 0 0 0
EDIT: forgot to add the "OT" to the subject
[ June 03, 2004, 14:56: Message edited by: alarikf ]