Sets-3
J.M.Basilla
Cryptography
Math 1
General Education Mathematics
Lecture 13
Julius Magalona Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Institute of Mathematics
University of the Philippines-Diliman
[email protected]
2010 Math 1
Main Problem
Sets-3
J.M.Basilla
Overview
Main Problem
Alice
message Bob
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
message
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Oscar
?
The science of secret writing
Sets-3
J.M.Basilla
The science of Secret Writing
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Steganography
Cryptography
hiding
scrambling
Monoalphabetic
Substitution
Transposition Substitution
anagram
ocw
wco
cwo
woc
cow
owc
Cryptography in World War I
The
communication
channel
Code
Cipher
word level
letter level
The alphabet
Main Problem of Coding Theory
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography should not be confused with Coding Theory.
Alice
message
Noise
Bob
?
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Noise
Main Problem of Coding Theory
Sets-3
J.M.Basilla
Overview
Cryptography should not be confused with Coding
Theory.
Storing
Alice
Information
Retrieving
Bob
Noise or Errors
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Noise
The sinking of Lusitania
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
I
In 1915, a German U-boat sanked Lusitania.
I
The German appeased Woodrow Wilson with a
promise of ”restricted submarine warfare”.
I
Americans remained neutral.
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
The Zimmermann Telegram
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
I
January 9, 1917. The German supreme high
command persuaded the then German Foreign
Minister Arthur Zimmermann to engage in an
unrestricted submarine warfare.
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
The Zimmermann message, decrypted and
translated
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
January 17, 1917. The British intercepted and
deciphered Zimmerman’s telegram to the German
Ambassador to the United States.
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
The Zimmermann message, decrypted and
translated
We intend to begin unrestricted warfare on the first of
February.
We shall endeavor in spite of this to keep United States
neutral. In the event of this not succeeding, we make
Mexico a proposal of alliance on the following basis: make
war together, make peace together, generous financial
support, and an understanding on our part that Mexico is
to reconquer the lost territory in Texas, New Mexico and
Arizona. The settlement in detail is left to you.
You will inform the President of Mexico of the above most
secretly, as soon as the outbreak of war with the United
States is certain and add the suggestion that he should, in
his own initiative, invite Japan to immediate adherence and
at the same time mediate between Japan and ourselves.
Please call the President’s attention to the fact that the
unrestricted employment of our submarines now offers the
prospect of compelling England to make peace within
months. Acknowledge receipt.
Zimmermann
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
The Americans joined Britain and France
I
I
I
February 1, 1917. The Germans engaged in
unrestricted submarine warfare.
February 23, 1917. Britain showed the message
intercepted in Mexico to US.
April 6, 1917. US joined Britain and France against
Germany.
Had the telegram never been intercepted or
never been published, inevitably the Germans
would have done something else that would
have brought us in eventually. But the time was
already late and, had we delayed much longer,
the Allies might have been forced to negotiate.
To that extent the Zimmermann telegram
altered the course of history...
Barbara Tuchman
American Historian,
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
The classical communication channel
Sets-3
Oscar
J.M.Basilla
?
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Alice
Encryption hidden message
decryption
Bob
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Secure channel
key generators
The Pigpen Cipher
Free masons
>The alphabet are the set of characters/fundamental unit
in writing a message.
A
N
J
A
B
K
L
B
C
O
P
C
Q
D
E
F
M
N
D
O
E
R
Q
H
I
P
R
F
G
S
T
G
U
H
I
V
J
W
W
S
K
X
U
T
X
Y
L
Y
M
Z
V
Z
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
An Example
Sets-3
Pigpen Cipher
A
B
C
J.M.Basilla
D
E
F
G
Overview
Main Problem
Cryptography is not Coding
H
I
J
K
L
M
N
History of
Cryptography
U
The
communication
channel
Cryptography in World War I
O
V
P
W
Q
X
Happy =
Carpe Diem
R
Y
S
Z
T
Monoalphabetic
Substitution
The alphabet
Calvin and Hobbes
Sets-3
J.M.Basilla
Overview
Main Problem
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet
Calvin:
Hobbes:
Calvin:
Hobbes:
”So, our secret code is ready”
”Let me see”
”I have assigned to each letter a completely random
number so that code becomes hard to break. The
letter A is 3.004.577.688, B is 28.731.5691/2”
”This must certainly be a really good code”
Main Limitation of Non mathematical
Monoalphabetic Substitution
Sets-3
J.M.Basilla
Overview
Main Problem
I
I
I
The comics strip captures the main difficulty of Non
mathematical Monoalphabetic substitutionmemorizing the rule of substitution or the
encoding/decoding keys.
Cannot be made complicated nor applied to an
message with plenty of characters in the alphabet.
Easy to attack using frequency distribution.
Cryptography is not Coding
History of
Cryptography
Cryptography in World War I
The
communication
channel
Monoalphabetic
Substitution
The alphabet