Cipher level F

Cipher code F was a Starfleet encryption code in use in the mid 2290s, unbroken by the Romulans as of 2296. During the mission to Obsidian, after detecting a Romulan Warbird in the area, Commander Uhura of the USS Intrepid II (Oberth class) ordered Lieutenant Duchamps send an encoded using cipher code F embedded in a false message using cipher code D, which had previously been broken.