File Encryption Tool

Improved prompt:

Design and implement a robust, client-side encryption tool using modern web technologies. The application should provide a user-friendly interface for encrypting and decrypting files on the client-side, ensuring data security without ever transmitting sensitive information to a server.

Technical Requirements:

1. Front-end Stack: Utilize HTML5, CSS3, and JavaScript to build the client-side application.

2. Encryption Library: Leverage the Web Crypto API for all cryptographic operations. Ensure all operations are performed entirely on the client-side.

3. Interface Design:

   • Create a drag-and-drop interface for file selection that supports multiple file uploads simultaneously.
   • Implement progress indicators to display the status of encryption and decryption processes.
   • Design a clean, intuitive layout with clear separation between encryption and decryption functions.
   • Include a password strength meter that calculates the entropy of user-provided passwords and enforces a minimum strength threshold.

4. Cryptographic Algorithms:

   • Use AES-256-GCM for the core encryption algorithm, providing both confidentiality and integrity.
   • Implement PBKDF2 with a strong salt and iteration count for key derivation from passwords.
   • Integrate secure random number generation for initializing encryption keys and salts.

5. File Processing:

   • Support batch encryption of multiple files simultaneously, utilizing multi-threading or web workers for parallel processing.
   • Implement streaming encryption for handling large files, processing them in chunks rather than loading them entirely into memory.
   • Ensure the encrypted files are downloadable with a custom file extension, e.g., ".aes256gcm".

6. Security Features:

   • Implement automatic clearing of sensitive data (keys, salts, passwords) from memory after each operation.
   • Include detailed logs of operations without storing sensitive information, focusing on non-sensitive metadata like file sizes and operation durations.
   • Provide secure key exchange for exporting and importing encryption keys, with proper security warnings and verifications.

7. Decryption Interface:

   • Create an intuitive interface for decrypting files, requiring the same password used for encryption.
   • Display clear verification messages for successful and failed decryption attempts.
   • Implement a mechanism to recover from interrupted decryption processes.

8. Performance and Usability:

   • Optimize the algorithm for performance in modern browsers, utilizing browser-specific optimizations where available.
   • Ensure the application works consistently across different browsers and devices.
   • Include clear instructions and tooltips for users unfamiliar with file encryption processes.

9. Documentation:

   • Write clear, detailed documentation explaining the cryptographic algorithms and security assumptions used in the application.
   • Include instructions for users on best practices for managing encryption keys and passwords.

Please provide a polished implementation that meets these specifications while maintaining a high level of security and usability.