The Technology and History of the Enigma Cipher Machine

1
TheTechnology and Historyof theEnigma Cipher
Machine

• Ralph_at_CipherMachines.com
• August 25, 2008

2
Agenda

• Enigma technology
• Enigma operating procedures
• Live demonstration
• Significance of Enigma in WW2
• Beginning of modern computing
• Maximum of settings

3
Enigma Machine What is it?

• Electro-mechanical cipher machine, simple in
  design yet powerful in capability
• Designed in Germany in 1918 for commercial use,
  adopted by German military in 1926

• Uses rotors and plugboard settings (the key) to
  encrypt each letter of a message with a different
  cipher
• Reflector design allows encryption and decryption
• Design has theoretical maximum number of settings
  (or keys) of 3 X 10114, far more than the
  number of atoms in the universe (1080)
• Germans accepted operational tradeoffs which
  reduced the number of settings to the still
  astronomical number of 1023 (see backup
  slides for math)
• 1023 means 100,000 operators, each checking one
  key setting every second would take twice the age
  of the universe to break the code yet the
  Allies succeeded by developing the 1st computer

4
Keyboard

• QWERTZ keyboard with only 26 letters - no
  numbers, space bar, etc.
• Pressing key first rotates 1 to 3 rotors then
  lights up a bulb
• Each letter is encrypted 7 to 9 times, the key
  changes for each letter
• No letter will encrypt to itself
• Note the serial plate below the V

5
Plugboard

• Cables changed as part of daily key
• Germans always used 10 cables, switching 20 of 26
  letters instead of varying of cables from 0-13
• Reduced of possible settings from 5.3 X 1014 to
  1.5 X 1014, but simplified operations

6
Rotors and Reflector
Notch by 04 means rotor on left advances on
letter D

• 3 rotors out of 5 available are changed daily,
  giving 5 X 4 X 3 60 possible positions for the
  3 rotors
• As part of the daily key, each rotor is set to a
  beginning alphabetic character, giving 263
  17,576 possible settings
• 1 to 3 rotors advance, changing the cipher after
  every keystroke
• Reflector (with red B) enables Enigma to
  encrypt / decrypt with the same key settings

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Light Bulb Panel

• Keyboard, plugboard and light panel all follow
  QWERTZ format
• Only method of output - no printing capability
• Light bulb under panel lights up a letter, which
  must be written down
• Latches on each side hold plastic filter to
  reduce light
• Operated by 4.5 volt battery or transformer from
  220V plug

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Wiring Diagram
Left Rotor
Middle Rotor
Right Rotor
Entry Drum
Reflector

6
7
8
times enciphered

5
2
3
4
Q
W
E
R
T
Z
I
O
U
Light Panel
A
S
D
F
G
H
K
J
Y
X
C
V
B
M
L
N
P
Q
W
E
R
T
Z
I
O
U
Keyboard
H
A
S
D
F
G
K
J
P
Y
X
C
V
B
M
L
N
Q
W
E
R
T
Z
I
O
U
A
S
D
F
G
J
1
K
H
Plugboard
P
Y
X
C
V
B
M
L
N
9
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Nazi Procedures for the Enigma

• Daily keys (settings for rotors and plugboard
  cables) were sent in a code book each month
  (longer for U-boats)
• Using the daily key, operators first sent a new
  key, then the text of the message in this new key
  nullifying letter frequency analysis
• The new key specified the 3 rotor positions, and
  was sent TWICE

• Some operators used the same keys for each
  message, such as girlfriends initials giving
  clues to solve the code
• Polish code-breakers exploited this shortcoming
  until 1939, when the Germans started sending the
  3 letter key ONCE and issued 2 more rotors

Using Enigma in the field
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Demonstration

• Demo how the Germans set up the Enigma with a new
  daily key, changing the rotors and plugboard
  cables
• Send a message using German military procedures
• Show the encrypted message, noting that each
  letter has a different cipher code and every
  message uses a different key after the first 6
  characters
• If each message used the same key as the daily
  key, then code-breakers could easily break the
  code using letter frequency analysis
• Decrypt that same message on the Enigma

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Shortcomings of the Enigma

• Due to the strength of the Enigma design, the
  Germans had complete confidence its security,
  even when faced with evidence of compromise
• The reflector design allowed encryption and
  decryption with the same settings, but also
  ensured no letter encoded to itself
• The notches on the rotors turn the rotor on its
  left after one revolution but each rotor was
  fixed on a different letter making each rotor
  unique
• Multiple or movable notches could have been used
  as another key but were not considered necessary

Panzer General Heinz Güderian on communications
truck with Enigma machine
12
Polish Success in Decoding Enigma

• In 1932, Germans accidentally sent an Enigma
  machine to Poland and sent an urgent diplomatic
  message to return it immediately
• Polish agents reverse engineered the Enigma
  overnight before returning it to Germany
• Enigma code was still not broken until the French
  bribed a German official to get keys
• This gave the Polish code-breakers enough
  knowledge to exploit the double sending of the
  key breaking the code in March 1933

Marian Rejewski Polish cryptographer

• Poles manufactured a Bomba 6 Enigma machines in
  series to speed the checking of codes for the 6
  combinations of 3 rotors
• Poles successfully decoded Enigma messages until
  1939, when the Germans quit sending the key twice
  and added 2 new rotors
• In 1939, Germany invaded Poland, Poles took
  Enigma secrets to France and Britain, finally
  disclosing their code-breaking success

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British Effort in Breaking the Code

• In 1939, UK began a major decoding effort in
  Bletchley Park, employing 11,000 people
• Effort led by Alan Turing, who built the Bombe -
  36 Enigmas in series to check settings

Bletchley Park Mansion

• Many settings were manually eliminated and only
  the remaining settings checked by the Bombe
  brute force wouldnt work
• Army and Luftwaffe messages were routinely
  decoded, the Naval Enigma was the greatest
  challenge
• British were careful to only act on intelligence
  that could have been uncovered from traditional
  sources

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U-Boat Peril

• Before the US entered the war, U-boats decimated
  Allied shipping, sinking about 60 ships per month
• U-boats roamed freely throughout Atlantic,
  forming wolfpacks to efficiently destroy
  convoys of supply ships for the UK
• Nazi strategy was to blockade the UK, hoping for
  a quick surrender
• Naval Enigma was initially the same as the Army
  version, but later, more complex versions were
  used with more rigorous procedures

• Naval Enigma messages were completely secure
  until May, 1941

The only thing that ever really frightened me
during the war was the U-boat peril - Winston
Churchill
U-Boat
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U-110

• The first U-boat boarded and code books recovered
  was U-110 in May 1941
• Captain died trying to scuttle his U-boat
• U-110 was sunk by British so Germans didnt
  realize their codes were compromised
• This single act was the turning point in the
  Battle of the Atlantic

Captain of U-110 Fritz Julius Lemp
Sinking of U-110

Enigma operator in U-110
HMS Bulldog British destroyer captured U-110
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Bombe the First Computer
Alan Turing Father of Computing
Bombe The First Computer

• Bombe was named for the clicking of the contacts
  in the machine, which sounded like the ticking of
  a bomb
• 210 Bombes were built in the UK, all were
  destroyed after WW2
• US employed NCR to build a faster version of the
  Bombe to decode the 4 rotor naval Enigma 121
  were built
• By the end of the war, the naval code was
  deciphered within 12 hours and the rest of the
  days messages were read in real time

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Battle of the Atlantic

• After breaking the Naval Enigma code, the British
  selectively protected some ships
• British knew when U-boats would surface for
  supplies, so they pretended to accidentally
  find and destroy them

US bombing of U-117 Aug. 1943

• In 1942, a 4th rotor was added to the Naval
  Enigma and 8 rotors were issued instead of 5 -
  making it more difficult to decipher
• An operator mistakenly sent the same message
  using old and new Enigmas, the new Engima was
  decoded before it went into service
• It was discovered that unarmed weather trawlers
  carried the Enigma and codes, not to encode
  messages but to read them giving the Allies an
  easy target for additional code books
• Early U-boat success turned to failure, 725 of
  1155 U-boats and 82 of 35,000 sailors never
  returned from sea
• Some estimate breaking the Enigma code shortened
  the war by 2 years, but another view is this was
  a key factor in the Allies victory

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Enigma After WW2

• The Enigma decoding success was a closely guarded
  secret, even after the war
• Despite 11,000 people working on the effort in
  Bletchley Park, plus thousands more in Poland,
  France and the US, the code-breaking success was
  not revealed until 1974
• About 100,000 machines were manufactured, most
  destroyed after the war since its significance
  was not understood
• Fewer than 200 are known to exist and a few turn
  up every year in ex-German soldiers basements,
  etc.
• Most are in museums but 70 are in private hands,
  32 in the USA
• Enigma machines are now a collectors item for the
  über geek - a standard Army Enigma has increased
  in value from 20K in 2000 to over 40K today,
  Navy versions sell for up to twice that price
• The last two Enigmas to trade on eBay varied in
  price from 85,000 in April 2006 to 30,000 in
  July 2007

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My Enigma Machine

• Bought at auction in Cologne, Germany in Nov.
  2002
• Entirely original, restoration of outer varnish
  and battery only
• Serial number plate reads A12760 / jla / 41
• A - Army version
• 12760 - serial number
• jla - code for location of manufacture, Berlin
• 41 - year of manufacture, the Berlin location
  started operations in Sept. 1941 and this is the
  first known Enigma from this facility

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My Enigma Machine

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Addendum

• Math showing the maximum number of settings both
  theoretically and as practiced by the Nazis

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Maximum Plugboard Settings
23
Maximum Rotor Settings
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Reflector Settings
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Theoretical Maximum Number Settings

• The total theoretical number of Enigma settings
  is thus the product of the 5 items on the
  previous 3 slides, or
• 3,283,883,513,796,974,198,700,882,069,882,752,
  878, 379,955,261,095,623,685,444,055,315,226,006
  ,433,615, 627,409,666,933,182,371,154,802,769,920,
  000,000,000
• Or 3.28 X 10114
• This number is far greater than the total number
  of atoms in the observable universe (1080)

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Theory vs. Practice

• The theoretical number of Enigma settings was
  never achieved in practice by the Germans. The
  number of settings the Allied Forces encountered
  for the standard 3 rotor enigma was
• 10 plugboard cables were always used, reducing
  the possible combinations to 150,738,274,937,250
• Only 5 rotors were issued, so selecting 3 out of
  5 is 5 X 4 X 3 60
• The initial settings of the rotors and the
  positions of the notches remain the same at
  17,576 and 676
• Reflector setting was known and remained
  unchanged 1
• The product of the above numbers is
  107,458,687,327,250,619,360,000 or 1023
• To test 1023 key settings, 100,000 operators each
  checking one setting every second would take
  twice the age of the universe to break the code