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World History Lecture Twelve (view source)
Revision as of 22:24, April 22, 2009
, 22:24, April 22, 2009→The Enigma: revised
===The Enigma===
===The Enigma===
In warfare, both sides use "ciphers" to encrypt their messages about troop movements and planned attacks in secret codes so that the enemy cannot eavesdrop and understand the communications. The National Security Agency is a super-secret branch of the U.S. Government staffed by mathematicians who seek better ways to protect American communications against enemy interception, and better ways to decode or decrypt the secret messages of the enemy to anticipate their next moves.
As an NSA report explains about World War II:<ref>http://www.nsa.gov/about/_files/cryptologic_heritage/publications/wwii/eavesdropping.pdf</ref>
:Two examples of famous ciphers from World War II are the Axis cipher machines, the German Enigma and the Japanese Purple (known to the Japanese as the 97-shiki O-bun In-ji-ki, or Alphabetical Typewriter ’97). Both machines substituted letters for plaintext elements according to daily settings (key)
for each machine. Interestingly, most ciphers used by all sides during the war
overwhelmingly were manual in nature. That is, they involved the use of paper
charts and key. Such a manual cipher was the double transposition cipher used by
German Police units to encrypt their reports about the massacres of Jews, partisans, prisoners, and Soviet commissars to Police headquarters in Berlin.
The Enigma was a portable cipher machine, roughly the size of a typewriter, which could encrypt and decrypt secret messages. It used electro-mechanical rotors to convert a message to a secret code, and then another machine could decode that same message and reveal the original message. This machine was commercially available beginning in the early 1920s. The Nazi German military version generated codes widely thought to be unbreakable.
The Enigma was a portable cipher machine, roughly the size of a typewriter, which could encrypt and decrypt secret messages. It used electro-mechanical rotors to convert a message to a secret code, and then another machine could decode that same message and reveal the original message. This machine was commercially available beginning in the early 1920s. The Nazi German military version generated codes widely thought to be unbreakable.
For others to break (decrypt) the code, they had to figure out how the Enigma functioned, the wiring of its rotors and its daily settings (both rotors and plugboard).
For others to break (decrypt) the code, they had to figure out how the Enigma functioned, the wiring of its rotors and its daily settings (both rotors and plugboard).
Nazi Germany used the Enigma before and during World War II to send messages about its military maneuvers. But in 1932 a 27-year-old Polish mathematician (specifically, a cryptologist) named Marian Rejewski had used advanced mathematics (permutation theory with some group theory) to secretly break (“crack”) the Enigma codes. He then helped design working “doubles” of the Enigmas that could find the keys necessary for decryption. By 1938 the Poles were decrypting most of the German messages, and the Poles shared their marvelous discovery with Great Britain and France.
Nazi Germany used the Enigma before and during World War II to send messages about its military maneuvers. But in 1932 a 27-year-old Polish mathematician (specifically, a cryptologist) named Marian Rejewski used advanced mathematics (permutation theory with some group theory) to secretly break (“crack”) the Enigma codes. He then helped design working “doubles” of the Enigmas that could find the keys necessary for decryption. By 1938 the Poles were decrypting most of the German messages, and the Poles shared their marvelous discovery with Great Britain and France.
This breakthrough enabled the Allies to anticipate German military maneuvers, although sometimes the Allies would allow an attack to occur successfully in order to avoid signaling to the Germans that their code had been broken. The Allied code-breaking effort was known as “Ultra”, as in “ultra-secret”.
This breakthrough enabled the Allies to anticipate German military maneuvers, although sometimes the Allies would allow an attack to occur successfully in order to avoid signaling to the Germans that their code had been broken. The Allied code-breaking effort was known as “Ultra”, as in “ultra-secret”.
At the end of the war, Allied General Dwight Eisenhower said that Ultra was “decisive” to the Allied victory over Germany. British Prime Minister Winston Churchill also declared, “It was thanks to Ultra that we won the war.” The breaking of the German codes prevented Germany from completely blockading Britain with U-boats and enabled the Allied forces to make key strategic decisions throughout the war.
At the end of the war, Allied General Dwight Eisenhower said that Ultra was “decisive” to the Allied victory over Germany. British Prime Minister Winston Churchill also declared, “It was thanks to Ultra that we won the war.” The breaking of the German codes prevented Germany from completely blockading Britain with U-boats and enabled the Allied forces to make key strategic decisions throughout the war.
===America Enters the War===
===America Enters the War===