Implementation of Caesar Cipher Program in Python

Overview

We will cover the Python implementation of the Caesar Cipher, a cryptographic technique used to encrypt and decrypt messages. If you are not familiar with this technique, it involves shifting the letters of a message by a certain number of positions. This technique was used by Julius Caesar to send confidential messages, and it is still relevant in modern cryptography. Through this article, you will learn how to implement the Caesar Cipher in Python and use it to encrypt and decrypt messages.

Introduction to Caesar Cipher in Python

Caesar Cipher is one of the most well-known and straightforward encryption methods in cryptography. The shift Cipher, Caesar's Cipher, Caesar shift, and Caesar's code, are some of its alternate names. Plain text is encrypted using this encryption method so that only the intended recipient can decipher it. Julius Caesar, who employed it in his communications, gave the approach its name.

With this encryption method, each letter in the text must be changed for a certain difference to encrypt our data. Let's imagine there is a letter "B," which becomes "C" with the left shift of 1, and "A" with the right shift of 1. Therefore, there is a difference of 1 and a text will follow the same path. Left and right shifts cannot be used simultaneously in the same text.

Let's have an example here, Think about receiving the message "IFMMP FWFSZPOF". What to interpret that as is crazy. So let's take the help of this diagram below to understand this text.

Now using this diagram drawn above we can decrypt our message "IFMMP FWFSZPOF" as shown below.

As you can see, our Cipher message starts with the letter I. (IFMMP FWFSZPOF). After going through the above-shifted alphabets we can encrypt that the letter H is converted to the Cipher character I. So after decrypting our message** "IFMMP FWFSZPOF"** the output is "HELLO EVERYONE".

Pre-requisites:

• For loop in Python
• ord in Python
• String in Python

Algorithm of Caesar Cipher in Python

The algorithm of Caesar Cipher holds the following features :

• Caesar Cipher Technique is a simple and easy method of encryption technique.
• Every letter in plain text is changed to a letter that appears a certain number of positions farther down the alphabet.

To understand this algorithm in a better way let's say we want to encrypt the text "HELLO EVERYONE". Then, what we can do is change every letter in the text with a new letter that has a fixed difference. If we want to left-shift the text by 1, we must replace each letter in the previous sentence with the letter that comes after it.

Plain text: HELLO EVERYONE

Cipher text: IFMMP FWFSZPOF

As of right now, the user cannot read this text without the decryption key. The decrypt key is nothing more than the understanding of how the letters were moved during encryption. We must right shift each letter by one to decipher this.

That was Caesar Cipher's fundamental idea. The algorithm to obtain an encrypted letter will be as follows if we use a mathematical approach:

e = (a + n) mod 26

where e represents the encrypted letter's place value, a is the actual letter's position value, and n tells us the number of shifts to be done for each letter.

On the other side, we'll use the following formula to decrypt each letter:

e = (a – n) mod 26

Implementation of Caesar Cipher in Python

Now after having an understanding of Caesar Cipher through proper examples and diagrams, let's take a look at the implementation part of this.

Code:

Output:

Explanation

Each character in plain text "HELLO EVERYONE" is read one at a time. Transform each character in the provided plain text by the given shift pattern and appropriate rule depending on how the text is encrypted and decrypted. Following the procedure results in the creation of a new string known as Cipher text.

Brute Force Approach to Break Caesar Cipher

There are several ways to crack the Cipher text. One such option is brute force, which includes testing every decryption key that might exist. For a hacker, this method requires little work but it is easy.

The following is how the Caesar Cipher algorithm hacking algorithm works:

Code:

Output:

In the above example, the hacker has used all the possible keys to fetch the relevant message among all of them. So after going through all the possible messages, the hacker found out the message "RAW THIS SIDE" was more relevant in comparison to all others. So we can say that 3 is used as a key to encrypt the message.

How to Decrypt Caesar Cipher in Python?

To decrypt the original text, we can build a function that will shift in the opposite direction. But we can make use of the module's cyclic cipher's property.

Cipher(n) = De-cipher(26-n)

Decryption can be performed using the same function. As an alternative, we will change the shift value to shifts = 26 - shift.

Function to decrypt a cipher text is given below:

Output