As afore seen codes and ciphers are as old as the mankind.
However, for the safety sake its application in manmade communications
started circa 2000 years ago.
Over the years codes were responsible for the fall, the rise
as well as the death of kings, queens and leaders.
THE VENGEANCE
OPERATION
Admiral Isoruko Yamamoto was a Japanese military leader.
He was responsible for planning the attack to Pearl Harbor
in December 7, 1941, pressing the USA to enter in the
WWII. His scheme for eliminating the U.S. fleet as a major
opponent led to the June 1942 battle of Midway, in which
the
Japan lost naval superiority in Pacific, forcing him to
reorganize his forces. In April 1943, he planned an inspection
tour to boost the morale of the Japanese forces located
in the Northern Solomon Islands. In this way he sent the
details of his visit whose message containing his itinerary
was intercepted and decrypted by the American Naval Intelligence
Service that had already broken the new and most complex
Japanese naval code JN 25.
Based in this cryptanalysis data, the Pacific naval forces
commander in chief admiral Chester Nimitz planned an air
ambush known as "vengeance operation". Thus,
on 7,44 h, April 18, 1943, admiral Yamamoto aircraft -
codename "Betty" by the allied forces, was shot
down in the jungles of the island of Bougainville, during
an air raid performed by a squadron of American P-38 fighter
planes that came from the 400 miles Henderson Field base.
Without a doubt the enforcement of the cryptanalysis techniques
changed the course of the war in Pacific.
|
The saga of Admiral
Yamamoto.
Courtesy: US Navy Historical Center USA.
THE DEATH THROUGH CYPHERS
|
Painting by Sergeant
Vaughn A. Bass, based on information provided by Lieutenant
Colonel Thomas G. Lanphier Jr illustrating the moment
that the admiral Yamamoto's "Betty" bomber
was shot down by the Colonel's Lanphier's P-38 fighter.
It depicts the intensive escort made by the famous
Japanese Zeke planes it could not avoid the success
of this air raid, that took place on April 18, 1943.
Certainly it was a direct consequence of the Japanese
messages deciphering made by the American Naval Intelligence
Service.
|
The death through the cyphers.
Courtesy: US Navy Historical Center USA.
Nowadays, codes and ciphers have many applications. Anyone
looking to access his bank account is submitted to use a code
or a cipher, generally known as a personal password.
Soon one's was aware of the importance to send messages, whose
real meaning is known by the sender and recipient only. For
historical allocation purpose, it began in the Renaissance,
when its theoretical basis was settled down.
Thus, Cryptography was born. In reality it is known as the
science of secret writing by using codes and ciphers.
In a code, codewords or code numbers replaces the word or
words that are found in a phrase, requiring the use of the
so famous and well known "code book".
In this way to decipher the message or the cryptogram it is
mandatory to have the codebook as without it, the message
seems unintelligible.
PLAIN TEXT
|
CODE NUMBER
|
CODEWORD
|
A
|
9213
|
OFHX
|
BRIGADE
|
5392
|
DAIN
|
SEND
|
5390
|
AMCE
|
TO
|
6788
|
IGZY
|
RADIORECEIVER
|
7492
|
PQLN
|
So, in the phrase: SEND A RADIORECEIVER TO BRIGADE, it is
encrypted as follows:
NUMERIC KEY |
KEY WORD |
6788 5390 7492 9213 5392 |
AMCE PQLN IGZY DAIN OFHX |
The main diference between a code and a cipher is that a
code operates on complete words or phrases and a cipher works
on single letters using the pinciple of transposition and
substitution.
In the military communications the ciphered message by transposition
is a more simple process. In other words it is an anagram,
which means a rearrangement of the letters of the plaintext.
An anagram (it is a Greek word
where ana- = "back" or "again", and
graphein = "to write"). When the subject
and the resulting anagram form a complete sentence, a
tilde (~) is commonly used instead of an equal sign; e.g.,
Semolina ~ is no meal. |
For instance, in a certain plain text the word: SECRET is
jumble to form the ciphering RSEETC.
In the substitution, firstly the alphabet is rearranged in
such away the letters are replaced by symbols, numbers or
even a different letter, where, for instance:
b=x e x=b, where de word, SECRET, becomes: HVXIVG.
PLAIN ALPHABET
|
CIPHERED ALPHABET
|
a
|
l
|
b
|
D
|
c
|
F
|
d
|
N
|
e
|
P
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
i
|
G
|
-
|
-
|
-
|
-
|
o
|
U
|
-
|
-
|
r
|
X
|
Bearing this aspect in mind, the word RADIO is encrypted
now as XINGU. Therefore, in the single cipher alphabet, as
per the aforementioned example, the cryptogram has a continuous
encrypted character, and certainly it does not offer a good
security level.
This means that in order to improve its disguising efficiency,
the cryptanalysts prefer to use the substitution procedure
through a poly alphabetic technique in such away instead of
each plaintext letter being represented by only cipher character,
it can be replaced by any one of the letters in an entire
alphabet.
In reality, enciphering technique derived from the well-known
Vigenère table, which simplifies to group the ciphered
alphabet that corresponds to each character of the plain alphabet.
For instance, in assuming that the word RADIO is the key selected
and that in the plaintext is composed only of the letter A,
in the encrypted message it looks like in the here under mentioned
table:
KEY
|
R A D I O R A D I O R A D
I O
|
PAIN TEXT
|
A A A A A A A A A A A A A
A A
|
ENCIPHERING
|
U D K S V U D K S V U D K
S V
|
In this way, the single letter A has now 5 encrypted meaning,
i.e. U-D -K-S-V. Meanwhile, if the selected key has 10 different
letters, the plain letter will take on 10 different encrypted
meaning that certainly increase the cryptogram security level.
Since the pioneering works of Giovanni Battista Porta and
Blaise de Vigenère back in the Renaissance, the Cryptography
has been improved giving birth of more advanced and complex
enciphering systems, where group of words and key numbers
are disguised previously.
Thus, the codebooks are small vocabularies or dictionaries
organized in alphabetic order that contain the equivalent
enciphered characters, which are grouped either in letters
or numbers according to the extension of the code used.
Like any bilingual dictionary, the codes books comprise a
section for enciphering and another one for deciphering and
to improve its efficiency codes errors were deleted previously
becoming an easy and quick task to use it.
However, in some complex transposition and substitution procedures,
and considering the urgency of the plain text enciphering,
generally required by the substantial volume of military communications
it is mandatory to simplify even more the code application
procedures.
Cryptologists at work.
In order to facilitate as much as possible the boring and
time consuming of the manual enciphering operations, the armed
forces cryptanalysis departments started in using a new technological
device as known as machine-assisted encryption.
|