SIGABA/ECM MARK II
Cryptography in WWII
The People Behind the magic
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William Friedman and Frank Rowlett
William F. Friedman
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Born 1891 in Kishinev
Moved to Pittsburg in
1893
B.S. and graduate work
in genetics
Joined Riverbank
Laboratories
Fell in love with
cryptography
Frank B. Rowlett
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Born 1908 in Rose Hill,
Virginia
B.A. from Emory and
Henry College
Hired by Friedman in
April of 1930
Worked as cryptologist
and cryptanalyst
Crucial in cracking
both PURPLE and RED
Development
Hebern Rotor Machine
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Built by Edward Hugh
Hebern in 1917
Not much success
Confidential
cryptanalysis by
Friedman in the late
1920s
M-134-T1
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Hebern’s machine was
unsuccesful
Friedman developed
M-134-T1
Utilized long paper
strips to create an
unpredictable stepping
Sigoo
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Let’s be honest, miles of
paper tape was not
effective
Limitations
Rowlett came up with
the idea of using rotors
to decide stepping
Attached to M-134-T1
SIGABA
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Rowlett and Friedman
ran out of money
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Went to Navy
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Ran with the idea
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Patent 70,412 in 1936
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First prototypes
released in 1940
1943, 10000 machines
in use
Colmar incident
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Army almost ruins it
Colmar Incident
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February 1945 during
the final US offensive
into Germany
2.5 Ton GMC truck was
stolen in Colmar France
Attracted the attention
of General Eisenhower
Cont.
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4 February 1945
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28th division arrive in
Colmar
5 February
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SIGABA arrives
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Left unattended
9 February
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Truck found
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Lower safe found in
Gressen River
20 February
The Machine
SIGABA
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Rotor based encryption
system
Utilizes 15 rotors
Produces a very
random stepping
pattern for the cipher
rotors
Rotor bank
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15 rotors
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5 Cipher Rotors (26
contact)
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5 Control Rotors (26
contact)
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5 Index Rotors (10
contact)
All set into rotor bank
Encryption
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1 rotor
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One input is energized
and follows wire to
corresponding output
5 rotors
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Follows similar process as
1 rotor, but outputs
become inputs
Cont.
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When a key is
energized on the
keyboard, it goes to
TWO places.
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Control Rotors (controls
stepping)
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Cipher Rotors (controls
encryption)
Stepping
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When a key is
energized, it is
encrypted through the
cipher rotors
The control and index
rotors will eventually
determine which
cipher rotors step
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The control rotors
function as a mixed up
odometer.
How they rotate:
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R1: LOCKED
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R2: 1 step/676 strokes
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R3: 1 step/1stroke
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R4: 1 step/26 strokes
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R5: LOCKED
Cont.
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Index rotor stepping:
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This is easy, they don’t
move after set up!
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Cipher rotor stepping…
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This is complicated
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Hold on
Cipher rotor stepping
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A key on the key board is energized.
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One path to cipher rotors other to control.
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The energized key becomes four inputs (F,G,H, and
I) to the control rotors
The four inputs work their way through the control
rotors
There are now four outputs on the left side of the
control rotor bank
Cont.
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These four outputs then
become inputs to the
indexing rotors
They are ORed into
groups in order to fit the
size of the index rotors
The inputs will then
work their way through
the index rotors
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There will be a maximum
of four outputs
Cont.
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The outputs are then
ORed at the output of
the index rotors
It is a binary function
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1: Corresponding cipher
rotor steps
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0: Corresponding cipher
rotor does not step
Phewww…
C
1
C
2
C
3
C
4
C
5
S
1
S
2
S
3
S
4
S
5
Statio Ever
y
nary
676
lett
ers
Ever
y
lett
er
Ever
y 26
lett
ers
Stat
iona
ry
I
3
I
4
I
5
V
+
I
1
I
2
Ciphe
r
text
Key space
Theoretical Key Space
Practical Key Space
Picture References
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http://en.wikipedia.org/wiki/File:William-Friedman.jpg
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http://www.ctcl.org/notables/alumni
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http://www.jproc.ca/crypto/hebern_1.html
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http://forum.xcitefun.net/colmar-france-most-beautiful-c
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http://www.jproc.ca/crypto/ecm2.html
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And from Dr. Mucklow’s lecture slides