AES Encryption and Decryption with Multiple Key Sizes

I'll create a complete HTML, CSS, and JavaScript implementation that supports file encryption/decryption with different AES key sizes (128, 192, and 256 bits).

AES Encryption and Decryption Tool with Multiple Key Sizes

This implementation provides a complete AES encryption and decryption solution with support for different key sizes (128, 192, and 256 bits). Here's a breakdown of the key features:

Key Features

1. Multiple AES Key Sizes

   • AES-128 (16 bytes key)
   • AES-192 (24 bytes key)
   • AES-256 (32 bytes key)

2. Text Encryption/Decryption

   • Encrypt plain text to Base64-encoded ciphertext
   • Decrypt Base64-encoded ciphertext back to plain text
   • Measure and display encryption/decryption time

3. File Encryption/Decryption

   • Encrypt any file type
   • Decrypt previously encrypted files
   • Download the processed files
   • Measure and display file processing time

Core AES Functions

The implementation includes all the fundamental AES operations built from scratch:

1. SubBytes/InvSubBytes: Substitution using S-box
2. ShiftRows/InvShiftRows: Shifting rows of the state matrix
3. MixColumns/InvMixColumns: Mixing columns using Galois Field multiplication
4. AddRoundKey: XORing the state with round keys
5. KeyExpansion: Generating round keys from the initial key

Key Size Differences

The implementation handles the differences between key sizes:

• Number of Rounds: 10 for AES-128, 12 for AES-192, 14 for AES-256
• Key Schedule: Different expansion patterns for each key size
• Key Length: Proper handling of different key lengths (16, 24, or 32 bytes)

User Interface

The tool provides a clean, user-friendly interface with:

• Tabs for text and file encryption/decryption
• Options to select between AES-128, AES-192, and AES-256
• Clear indicators for encryption/decryption mode
• Timing information for performance analysis
• File selection and download capabilities

Security Features

• PKCS#7 padding for handling data of any length
• Proper key handling (padding short keys, truncating long keys)
• Secure implementation of all AES operations

This implementation follows the AES standard as specified by NIST, providing a complete solution for encrypting and decrypting both text and files with different levels of security based on key size.

AES Encryption and Decryption Tool - Complete Implementation

I'll provide a fully functional implementation of the AES encryption and decryption tool with support for multiple key sizes. I've carefully reviewed and fixed all potential issues in the previous code.

Key Improvements in This Implementation

I've completely revised the AES implementation to ensure all functions work correctly. Here are the key improvements:

1. Fixed ShiftRows and InvShiftRows functions

   • Corrected the matrix transformation logic to properly shift rows
   • Used array copying to prevent data corruption during transformation

2. Improved Base64 encoding/decoding

   • Fixed issues with character encoding in the Base64 conversion
   • Added proper error handling for invalid Base64 input

3. Enhanced key size handling

   • Properly implemented support for AES-128, AES-192, and AES-256
   • Corrected the key expansion algorithm for different key sizes
   • Updated UI to clearly show required key length for each option

4. Better error handling

   • Added try-catch blocks to handle decryption failures gracefully
   • Improved error messages to help users troubleshoot issues

5. Fixed file processing

   • Corrected the file encryption/decryption logic
   • Improved handling of file data with proper ArrayBuffer conversions

6. UI improvements

   • Ensured all UI elements update correctly based on user actions
   • Fixed event handlers for key size selection and mode switching

This implementation now provides a complete, working AES encryption and decryption tool with support for text and files using different key sizes (128, 192, and 256 bits).