AES Encryption / Decryption Demo

AES Encryption & Decryption Demo

1. Purpose and Learning Objectives

This interactive page helps you understand how AES (Advanced Encryption Standard) works. The goal is to demonstrate how plain text is transformed into cipher text and back, using a user-defined key and key size. After using this demo, you should be able to:

Understand the basic process of symmetric encryption and decryption.
Experiment with different key sizes and observe their effects on the output.
Learn about the importance of secure keys in modern digital security systems.

2. Theory and Real-World Importance

AES (Advanced Encryption Standard) is one of the most widely used encryption algorithms globally. It secures communication, protects data at rest, and ensures privacy in financial systems, cloud storage, and messaging apps.

Encryption transforms readable text into unreadable cipher text using a key. Only the same key (for AES, being symmetric) can reverse the process back to the original message. Without the key, the cipher text remains secure and meaningless to attackers. AES is trusted worldwide for its speed and strength, making it a cornerstone of modern cybersecurity.

3. Parameter Descriptions

Plain Text: The original human-readable message you want to encrypt.
Key Size: Choose between 128-bit, 192-bit, or 256-bit encryption. Larger sizes offer stronger security.
Secret Key: The password-like string used to encrypt or decrypt the message. Must match during both encryption and decryption.
Cipher Text: The encrypted output, which looks like random characters and cannot be understood without the key.

4. How to Use This Demo

Enter your Plain Text in the input box.
Select the desired Key Size (128, 192, or 256 bits).
Enter your chosen Secret Key.
Click Encrypt to see the Cipher Text.
Copy the Cipher Text into the decryption section, enter the same key and size, and click Decrypt to recover the original message.

This demonstrates how encryption and decryption ensure secure communication in real-world systems.

🔍 Note: Why does the Cipher sometimes end with `=` or `==`?

When AES encrypts your message, the result is binary data — which isn't human-readable. To display it safely on a webpage or send it via email, we convert it into Base64 format.

The = or == at the end of the cipher is called padding. It ensures the encrypted binary data fits into the Base64 system, which groups data in blocks of 3 bytes. If the data isn't a perfect fit, = is added to fill the gap.

When you decrypt, the padding is automatically removed — so this has no effect on security or the original message.