Preserving History Through Code- Julius Caesar's Shift Cipher

Gaius Julius Caesar

From Wikipedia, the free encyclopedia
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.

Julius Caesar (100-44 BCE)

Source: Wikipedia

Caesar cipher using a left rotation of three places

Expectations

Plain : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: XYZABCDEFGHIJKLMNOPQRSTUVW

Plaintext : THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
Ciphertext: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

The action of a Caesar cipher

Source: Wikipedia

Caesar cipher disk was invented over a millemium after Julius Caesar

But we would borrow Alberti's disc to also visualize the Caesar's Cipher

CipherDisk2000 invented by Leon Battista Alberti 1404 - 1472

Source: Wikipedia

Caesar cipher using a left rotation of three places

With a left shift of 3, D would be replaced by A, E would become B, and so on.

The cipher disk illustration was inspired by Alberti's cipher disk, although his disk had the outer disk as the rotating disk and it was also in the reverse order compared to the inner disk.

CipherDisk in 0 position 0 Shift

Cipher disc 3 left rotations

Focus

This caesar cipher program encrypts only uppercase letters and no other characters. Modelled closely to the caesar cipher used before common era.

Install

pip install jc-cipher

Run in command/terminal

jc-cipher

Import modules

from caesar_cipher import encryption as ce
from caesar_cipher import decryption as de