Alphanumeric Square Cipher

A web-based interactive tool to encrypt and decrypt messages using the 6x6 Alphanumeric Square Cipher. This cipher supports both letters (A-Z) and digits (0-9), making it suitable for alphanumeric messages.

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Features

• Encrypt / Decrypt text with a secret key.
• Interactive 6x6 grid showing the cipher table.
• Step-by-step visualization of digraph processing.
• Automatically handles repeated letters and odd-length text using filler X.
• Fully responsive design using Bootstrap.
• Highlights letters being processed in real-time.

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How It Works

1. Generate Grid:

   • Create a 6x6 grid with letters A-Z and digits 0-9.
   • Start with unique characters from the secret key (row-wise).
   • Then insert numbers (0–9) and alphabets in the pattern: digit → two alphabets → digit → two alphabets → ...
   • Skip duplicates.
   • Continue until the 6×6 grid (36 slots) is filled.

2. Prepare Text:

   • Divide plaintext into digrams (pairs of letters).
   • If letters repeat in a pair or the length is odd, insert X as filler.

3. Encryption / Decryption Rules:

   • Same Row: Shift left (encrypt) or right (decrypt) by 2 positions.
   • Same Column: Shift up (encrypt) or down (decrypt) by 2 positions.
   • Rectangle: Swap the columns of the two letters.

4. Combine Results:

   • Combine processed digrams to produce the final encrypted or decrypted text.

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Demo

• [Live Demo Link]

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Installation

1. Clone the repository:

git clone https://github.com/SURIYA-PRAKASH-E-S/alphanumeric-square-cipher.git
cd alphanumeric-square-cipher

2. Install packages

npm install

3. Run

 npm start

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