Naval Intelligence--Finding the Enemy, Hiding your Forces

• Discussion Questions:
• Is an "unbreakable" code possible?
• Is it possible to "hide" coded transmissions?
• How do you balance the need to communicate with the need to be invisible to easedropping?
  
• Technical Issues and the Role of IT: Cryptography, Cryptanalysis
• Heroic Codebreaking: Enigma, the Battle of the Atlantic, and the Development of the Computer
• Codebreaking in the Pacific: Intelligence successes at Midway
• Technology and the Battle of the Atlantic
• Airborne Radars, High Frequency Direction Finding

• Background on Signals Intelligence/19th Century Technology
• Cryptography
• Radar
• Radio Navigation
  

Background Readings from The Oxford Companion to WW II:

Code Breaking/Signals Intelligence

• Atlantic, Battle of the, pp. 49-54 (particularly the discussion on ULTRA, pp. 53-54);
• B-Dienst, pp. 91-92;
• Bletchley Park, p. 10;
• Electronic Warfare, pp. 258-260;
• ENIGMA, p. 265;
• Eureka, pp. 266-267;
• Geheimschreiber, p. 340;
• Germany: Intelligence, pp. 376-377;
• Huff-Duff, pp. 429-430;
• Japan: Intelligence, pp. 493-494;
• MAGIC, pp. 552-555;
• MI6, pp. 581-584;
• Midway, Battle of, pp. 585-586;
• Naval Intelligence Division, pp. 606-607;
• Signals Intelligence Warfare, pp. 781-785;
• UK: Intelligence, pp. 900-901;
• ULTRA, pp. 910-917;
• USA: Intelligence, pp. 938-939;
• Y Service, p. 1011;

Navigation

• Electronic Navigation Systems, pp. 256-258;
• H2S, p. 411;

Radar

• Britain, Battle of, pp. 124-127;
  
• Cavity Magnetron, pp. 155-156;
• Radar, pp. 717-721;

Radio

• Radio Communications, pp. 721-724;

Miscellaneous

• Scientists at War, pp. 766-768;

Question for Discussion:

• Radio
• Radar
• Atomic Bomb
• Precision Bombsight
• Jet aircraft
• Ballistic Missile
• Aircraft Carrier

Exercise #1:

Consider the following encrypted message:

A D Q J D K D X C N M N S S Z J D K H E D S N N R D Q H N T R K X X N T V H K K M D U D Q F D S N T S N E H S Z K H U D

Our spies have been able to uncover three things about this message. First, the message includes no punctuation including spaces between words. Second, we know that the code is a simple letter substitution cypher, that is, a given letter of the alphabet is always replaced by the same letter when the message is encrypted. And third, the word "Berkeley" is embedded in the message.

By the way, we know the plaintext is in English, so the following table of letter frequencies in English may be of interest to you:

If you successfully decode the message by the next class meeting, you will win a FREE lunch with the course instructors! Good luck!

Exercise #2:

The web site http://www.qufaro.demon.co.uk/emachines/enigma.htm is a very nice Enigma machine simulator. Follow the instructions on the web site to set-up the machine to decrypt the German message. What plaintext message do you get in response?