Richard Maibaum and Paul Dehn
Richard Maibaum wrote almost as much Bond as Ian Fleming did. He wrote thirteen lucky Bond films, from Dr. No in 1962 to License to Kill in 1989. Of course, Goldfinger is included in that number.
Maibaum is arguably a better writer than Fleming, whose novels, including Goldfinger, often include improbable concepts and plot holes you could drive an Aston Martin through sideways. It was Maibaum who changed Goldfinger's plot from robbing Fort Knox—a virtually impossible task—to nuking it—a much more sinister action (source).
Paul Dehn, called in to polish Maibaum's screenplay, is credited with penning the explosive opening sequence. In fact, it may have been inspired by a real-life WWII mission in which a secret agent donned a wetsuit to sneak into Nazi-occupied Netherlands. Once inside enemy territory, he stripped off the suit to reveal a tuxedo underneath.
Dehn, an intelligence officer at that time, likely knew of the mission, and he shared his top-secret intelligence with us by writing it into Goldfinger (source). Maibaum may be top billed, but Dehn is closer to being an actual honest-to-goodness spy.