Cryptography

Before the Age of Radio, much more difficult to intercept cable traffic

Radio potentially places large numbers of encrypted messages in the hands of the cryptanalysts
This is the key to breaking the code!

British Admiralty Room 40: Codebreaking Room

Enigma Machine

Existence of ULTRA {"Very Special Intelligence") first revealed in 1974! Changed completely the way we view the history of WW II

Combined encoding/decoding machine
Five rotor system, three in use at any time
How it worked and why it was hard to crack
Use of per message keys makes analysis difficult
But patterns provide the way in: doubly encrypted message keys
Poles reverse engineer a stolen Enigma machine
Invention of the Bombe: mechanical device to exhaust all enumerations
New Enigma stumps the Poles who turn to the British (1939)

Bletchley Park
Japanese Codes

Page last modified 28 January 2003, by Randy H. Katz, randy@cs.Berkeley.edu