Transcript The Cracking of Enigma in World War II

The cracking of Enigma
in World War II
CS 4235 Project 1: Security Events - Threats and Vulnerabilities
John Bibb
Harry Caplan
Abhishek Chhikara
Vladimir Grantcharov
Aditi Kulkarni
Nigel Lawrence
Andrew Muldowney
Hou Nguyen
Sofia Tania
What is Enigma?
rotor machine used for the
encryption and decryption of secret
messages
 Developed in early 1920s
 Combination of mechanical and
electrical subsystems
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• Keyboard
• Rotating disks (“rotors”)
• display lamps
What happened?
Cracking the Enigma
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Enigma has so many possibilities, that an important aspect of breaking them, is
deducing their logical structure.
Enigma generated a polyalphabetic substitution cipher with a long period. Given
three single-notched rotors, the period was 16,900 (= 26 × 25 × 26).[7]
A letter could never be encrypted to itself. This property was of great help in using
cribs and could be used to eliminate a crib in a particular position. It was this feature
that the British mathematician and logician Alan Turing would exploit in designing the
British bombe.
A second Enigma weakness was that the plugboard connections were reciprocal, so
that if A was plugged to N, then N likewise became A.
A number of the officially-specified procedures for using Enigma also provided
avenues for attack. Thus, for machines where there was a choice of more rotors than
there were slots for them, a rule stipulated that no rotor should be in the same slot in
the scrambler as it had been for the immediately preceding configuration. Also, no
wheel order could be repeated on the monthly setting sheet.
It has been suggested by some who worked at breaking Enigma at Bletchley Park
that the Enigma should have been unbreakable in practice, had its operating
procedures been better thought out and had its operators been less ill-disciplined.
http://upload.wikimedia.org/wikipedia/commons/6/6c/Enigma-action.svg
http://enigmaco.de/enigma/enigma.swf Working Model
Bomba
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Designed about October 1938 by Polish Cipher Bureau : Bomba
Each bomb essentially constituted an electrically-powered aggregate of six
Enigmas and took the place of some one hundred workers
Using the knowledge that the first three letters of a message were the same
as the second three, Polish mathematician–cryptologist Marian Rejewski
was able to determine the internal wirings of the Enigma machine and thus
to reconstruct the logical structure of the device.
In mid-November 1938 the bombs were
ready, and the reconstructing of daily keys now took
about two hours.
Up to July 25, 1939, the Poles had been breaking
Enigma messages for over six and a half years
without telling their French and British allies.
Bombe
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On December 15, 1938, two new rotors were introduced.
Creator of Bomba: "we quickly found the [wirings] within the [new rotors], but [their]
introduction...raised the number of possible sequences of drums from 6 to 60...and
hence also raised tenfold the work of finding the keys. Thus the change was not
qualitative but quantitative.
A bombe would consist of a number of these sets of rotors wired up according to a
menu prepared by codebreakers. At each position of the rotors, an electrical test
would be applied. For a large number of the settings, the test would lead to a
logical contradiction, ruling out that setting. If the test did not lead to a logical
contradiction, the machine would stop and ring a bell, and the candidate solution
would be examined further, typically on a replica of the German Enigma machine,
to see if that decryption produced German.
Typically, there were many false matches
before the correct match was found.
Designed by Alan Turing
Eventually over 200 Built by both
US and British Forces
Also built to contend with late model
4 rotor Enigmas
What was the impact?
Impact
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Germans thought ‘Enigma’ unbreakable
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Used for all top secret communication
Dutch Idea -> German Spy -> French Spymasters -> British +
French + Polish Efforts -> Breakthrough by Poland -> Later Britain
From 1933 – 1940
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Marginal Impact
The Breakthrough
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Year 1941 & beyond
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Allies’ Mediterranean fleet defeated the Italians at the Battle of
Matapan
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Allies gained important advantage in North Africa
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German U-Boat program brought to standstill
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Allies detected German round-up near Greece
90% European Intelligence summaries provided to US based on
Enigma
Larger context – “Information is Power”
Repercussions
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Undermined Axis offensive
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May have ended the war early
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Contributed to the eventual Allied victory
Why did this attack
succeed?
Elements of Enigma
Plaintext
 Algorithm
 Key
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It takes all three elements to
perform the decryption.
Getting The Plaintext
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Infrastructure – ‘Y’ stations
Getting The Algorithm
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The role of mathematicians
Marian Rejewski
Photo from Wikipedia
Getting The Key
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The role of mathematicians
Getting The Key
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Clues based on patterns in messages
• Opening
“Spruchnummer” (Message Number)
 “An die Gruppe” (To the group) – Air Force
messages
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• Content
Weather reports
 “Keinebesondere Ereignisse” (Nothing to report)
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Duplicate messages
What happened in
the aftermath?
Perspective of Nazis
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After the code was broken, the Nazis were
unwilling to see the evidence of it as a breaking
of the code rather, they assumed that the British
simply had exceptional spies who were leaking
information. Thus they concentrated their efforts
on finding these spies, instead of adapting their
code further.
http://cultureandcommunication.org/deadmedia/index.php/Enigma_machine#Aftermath
Consequences
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Hitler postponed invasion of Britain until spring
1941, after a failed invasion in Oct 1940.
Significance of Codebreak
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It is estimated that the success of the efforts to
code break the German Enigma machine helped
The Allies defeat Nazi Germany two years
earlier than they would without it. This saved
countless lives, and making it one of the most
successful intelligence operations in history.
Popularity of the Event
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The Enigma intercepts came to be known by the
codename ULTRA and while they were perhaps
not directly responsible for winning the war as
sometimes credited, the information provided by
the Bletchley Park cryptanalysts certainly
shortened the war and saved many lives.
What was done to
make systems less
vulnerable to this
kind of threat?
Modification Before WWII
• Added two rotors
• Operators stopped sending individual
message settings twice at the start of each
message
• Eliminated the original method of attack
Modifications During WWII
Occasionally added new rotors, but never
on a widespread scale
 Triton
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New version of Enigma
Had 4 wheels instead of 3
What chapter in the
book will be helpful
in understanding
this event?
Chapter 2 - Elementary Cryptography
Sources
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Marian Rejewski’s photo
http://en.wikipedia.org/wiki/File:MR_1932_sma
ll.jpg
http://www.enigmahistory.org/main.html
http://www.ams.org/featurecolumn/archive/eni
gma.html
http://www.iwm.org.uk/upload/package/10/eni
gma/enigma9.htm
http://math.usask.ca/encryption/lessons/lesson
00/page8.html
http://library.thinkquest.org/28005/flashed/tim
emachine/courseofhistory/bombe.shtml
http://plus.maths.org/issue34/features/ellis/