The part of Cryptonomicon that caught my attention was Lawrence Waterhouse's attempt to solve the cipher, or "mathematical exercise" given to him and others by Commander Schoen. Schoen writes out the cipher, a list of 5 groups each with 5 numbers. The numbers are either 1 or 2 digits. Waterhouse instantly recognizes that the greatest number provided is 25, thus he assumes that the numbers must represent the letters in the alphabet. He then decides to run a frequency analysis test using the numbers on the board and realizes the number 18 occurs 6 times. Waterhouse then makes an assumption that the number 18 must be the letter E so he mentally substitutes the letter E into the cipher. Next, Waterhouse observes that the opening 4 numbers are '19 17 17 19'. He then knows that if 19 is a vowel, 17 must be a consonant or vice versa, and since 19 is twice as common in the cipher, he assumes that 19 is a vowel (specifically A). Waterhouse then proceeds by using the context of the message as provided by Commander Schoen earlier. Schoen had said that the message was intended for a naval officer. Using this, Waterhouse was able to guess that the first word was ATTACK. Immediately, he saw the rest of the cipher decrypt before his eyes so he stood up and stated his findings emphatically. The message read: "Attack Pearl Harbor December Seven"
The methods Waterhouse used to solve the cipher reminded me of the discussion we had earlier than year about the use of intuition to solve puzzles. Waterhouse used problem solving techniques and pure logic to decrypt the cipher. By assuming the first word was 'ATTACK' and recognizing that the numbers represented individual letters in the first place, Waterhouse demonstrated the problem solving techniques we have all acquired through basic learning.