Actually, after having met a navy launch officer, I learned that the US Navy, at least, has REDUCED security. You no longer even need to enter a code to launch. You just select a missile on your console and pull a little trigger and it starts the automated launch sequence. No checks at all, no security.

Two experienced launch officers are now sitting in brig because they were so shocked and alarmed by this new design that they decided to defy their orders and change their system back to the old, secure launch method.