8.6.1.1 - CODES AND CYPHERS - THE ORIGIN OF CRYPTOGRAPHY

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.