The orders arrive encrypted into groups of five random-looking letters, printed out on the blue tissue paper that is used for top-secret cablegrams. The message has been encrypted in Washington using a one-time pad, which is a slow and awkward but, in theory, perfectly unbreakable cipher used for the most important messages. Waterhouse knows this because he is one of the only two persons in Pearl Harbor who has clearance to decrypt it. The other one is Commander Schoen, and he is under sedation today. The duty officer opens up the appropriate safe and gives him the one-time pad for the day, which is basically a piece of graph paper covered with numbers printed in groups of five. The numbers have been chosen by secretaries in a basement in Washington by shuffling cards or drawing chits out of a hat. They are pure noise. One copy of the pure noise is in Waterhouse’s hands, and the other copy is used by the person who encrypted this message in Washington.