Your Cryptography

POLYBIUS SQUARE

[INTRODUCTION]
Polybius Square was originally conceived by the Greek historian Polybius in the 2nd century B.C., and is one of the simplest cipher in cryptography.

[ALGORITHM]
The polybius Square is a table that translates letters into numbers. To give a small level of the encryption, the table used in Polybius Square (see the attached photo) can be randomized and shared with the recipient. In order to fit the 26 letters of the alphabet into the 25 spots created by the table, the letters “I” and “J” are usually combined.

[ENCRYPTION]
To encipher a message, you replace each letter with the row and column in which it appears. For example, the letter A will be encrypted as 11; letter B will be encrypted as 12.

[DECRYPTION]
To decipher a message, you find the letter that intersects the specified row and column.

LECTURE #9: NAVAJO CODE
[INTRODUCTION]
There is no quite clear definition of what is the Navajo Code. Yet the code itself could be also named as Navajo language. Navajo is a complex language and one that hadn't really been translated into English by the mid-20th century. The language seemed to be the perfect option as a code because it is not written and very few people who aren’t of Navajo origin can speak it.
[BACKGROUND]
Back in the first World War, telephone technology were just emerging in terms of warfare strategy and, to keep their messages secret, some military squads used Amerindian soldiers speaking their native languages to relay communications. This was not a widespread practice, but did play a major role in a few American battles in France.
Then in 1941, the United States of America was drawn into a second World War with the bombing of Pearl Harbor. As America started preparing its military and entered the war, one major concern was protecting the secrecy of their military communications. A solution was presented in 1942 by World War I veteran Philip Johnston. Johnston had grown up on a Navajo reservation and, although not Navajo himself, had heard about the success of Amerindian telephone messengers in WWI. He proposed to the Navy that their military codes be based around the Navajo language. It was a perfect solution. Navajo is a complex language and in 1942 it hadn't really been studied by Europeans or Americans, so there were no printed dictionaries or translation guides. The only people who spoke Navajo were, simply enough, the Navajo.
[SETTING UP THE CODE]
Alongside with this, the Marine Corps planned to construct a lexicon of Navajo terms to replace otherwise untranslatable English words, thus removing any ambiguities. The trainees helped to compile the lexicon, tending to choose words describing the natural world to indicate specific military terms. Thus, the names of birds were used for planes, and fish for ships. Even though the complete lexicon contained 274 words, there was still the problem of translating less predictable words and the names of people and places. The solution was to devise an encoded phonetic alphabet for spelling out difficult words.
Within eight weeks, the trainee code talkers had learned the entire lexicon and alphabet, thus preventing the need for codebooks, which might fall into enemy hands. For the Navajos, committing everything to memory was trivial. They called the Navajo language a “weird succession of guttural, nasal, tongue-twisting sounds . . . we couldn’t even transcribe it, much less crack it.” The Navajo code was judged a success.
[NAVAJO ALPHABET CODE]
In addition, an alphabet system (see pictures on the post) was also developed by the Code Talkers. It would be used to spell out some of the words not found in Navajo vocabulary. The first letter of a Navajo word corresponded with one of the 26 letters in the English alphabet. Several different words were chosen to represent the more commonly used letters in order to make the code even more secure.
[NAVAJO VOCABULARY]
Kindly see the attached pictures to this lecture.
For more expounded reference, see this link: https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/n/navajo-code-talker-dictionary.html