using a copy of the romantic novel All This and Heaven Too and a sophisticated process that generated messages full of garbled letters instead of numbers. Each spy had been assigned a unique identification number, such as 7. To encrypt a message, the spy would take that day’s date, add the number of the day and the month to his identification number (for a January 10 message he would add 1 + 10 + 7 = 18) and turn to the resulting page
