Caesar Cipher Tool Documentation

Table of Contents

1. Project Overview
2. Installation
3. Usage
4. Encryption Algorithm
5. Examples

Project Overview 📝

The Caesar Cipher Tool is a web-based application that enables users to encrypt and decrypt messages using one of the earliest known encryption methods. The tool implements the Caesar Cipher, a substitution cipher that shifts each letter in the plaintext by a fixed number of positions down the alphabet. Built to focus on educational value and user experience, it offers a user-friendly interface for understanding basic cryptographic concepts.

Installation ⚙️

To install and run the Caesar Cipher Tool locally, follow these steps:

1. Clone the project repository:

git clone https://github.com/RobCyberLab/Caesar-Cipher-Tool.git

2. Navigate to the project directory:

cd src

3. Open the index.html file in your preferred web browser.

Usage 📖

1. Access the Caesar Cipher Tool by opening index.html in your web browser
2. The interface presents two main sections:
   • Input Section
     • Enter the text you want to process
     • Select operation mode (Encode or Decode)
     • Set the shift value (1-25)
     • Click "Apply" button
   • Output Section
     • View the processed text result
     • Use "Copy" button to copy the result
3. The application will display:
   • The encoded/decoded result in the output area
   • Any error messages if input validation fails

Encryption Algorithm 🔐

The Caesar Cipher implementation includes distinct handling for letters and numbers:

Letter Processing

• Case-sensitive processing
• Modulo 26 operation for alphabet bounds
• ASCII code manipulation

// Letter Shifting
let code = char.charCodeAt(0);
let baseCode = char === char.toUpperCase() ? 65 : 97;
code = (code - baseCode + shift) % 26 + baseCode;
char = String.fromCharCode(code);

Number Processing

• Modulo 10 operation for digit bounds
• ASCII adjustment for numeric values

// Number Shifting
char = String.fromCharCode((char.charCodeAt(0) - 48 + shift) % 10 + 48);

Examples 📌

Example 1: Basic Letter Encryption

Input:

hello

Shift: 3 Output:

khoor

Example 1: Encoding "hello" with a shift of 3

Example 2: Basic Decryption

Input:

khoor

Shift: 3 Output:

hello

Example 2: Decoding "khoor" with a shift of 3

Example 3: Mixed Case with Punctuation

Input:

Hello, World!

Shift: 5 Output:

Mjqqt, Btwqi!

Example 3: Encoding "Hello, World!" with a shift of 5

Example 4: Letters and Numbers

Input:

Cipher123

Shift: 7 Output:

Jpwoly890

Example 4: Encoding "Cipher123" with a shift of 7

Note: The application includes several features to enhance usability:

• Case preservation for letters
• Special character preservation
• Number shifting with modulo 10
• Input validation
• Copy to clipboard functionality
• Real-time error messaging

These features ensure a smooth user experience while maintaining the educational value of the classical Caesar cipher implementation.