How are nukes launched By password button keys?

Answer 1

While I do not know the exact procedures (they would be classified at least Secret-L anyway and I have never had -L clearance) here are some steps that I know of in the US missile launching procedure for missiles carrying nuclear warheads:

• President decides launch is necessary and uses "football" to select targeting, number to launch, and other battle parameters.
• "Football" issues cryptographically coded PAL (Permissive Action Link) data to allow arming of warheads on selected missiles.
• Launch orders are encrypted with daily passwords and sent to selected silos and submarines.
• Silos and submarines receive orders and PAL data.
• In each silo and submarine there are two missile launch control officers on duty at all times, each with his own launch control station on opposite sides of the room so that one cannot operate both stations.
• Each launch control officer independently decrypts the orders and gets his "personal" password.
• The two officers each go to their classified materials safe and get the password books and master launch keys.
• Each officer looks up the password for the day in his book. If it does not verify he locks everything back up in his safe. If it verifies he tells the other officer he has a valid order and takes his master launch key to his station.
• With both officers at their stations they can select missiles to launch and send them the PAL data to arm the warheads.
• If the warhead's PAL does not verify the decrypted PAL data it will inhibit arming and nothing can be done until the PAL is removed and factory reset, in some instances the PAL may destroy the warhead in silo by triggering a single detonator to prevent any nuclear yield. If the warhead's PAL verifies the decrypted PAL data it will arm the warhead.
• If all has gone well, both officers insert their master launch keys and turn them simultaneously.
• If the keys were turned simultaneously (within a few seconds at most), the selected missiles launch.