File Encryption Tool

I'll build a secure file encryption tool with a modern drag-and-drop interface using HTML5 and the Web Crypto API. The system will implement AES-256-GCM encryption with PBKDF2 key derivation (using 100,000 iterations and random salt), batch processing for multiple files, and chunked streaming for large files to avoid memory issues. Password strength will be enforced through entropy calculation, requiring at least 50 bits of entropy, and all sensitive data will be automatically cleared from memory using crypto.getRandomValues() overwrites.

I can create this encryption tool, though I want to be transparent about its security boundaries. Client-side JavaScript encryption provides good privacy for file storage/transfer, but cannot protect against malicious code injection or browser compromises. For the implementation, I'd use 1-2MB chunks for streaming, PBKDF2 with at least 100,000 iterations (310,000 is OWASP's current recommendation), and ensure all ArrayBuffers containing sensitive data are overwritten before garbage collection.

The tool will leverage the Web Crypto API's crypto.subtle.encrypt() method with AES-256-GCM mode, providing authenticated encryption. PBKDF2 key derivation will use SHA-256 with configurable iterations (default 100,000 per NIST SP 800-132). For large files, the FileReader.readAsArrayBuffer() method will process data in chunks, with each chunk encrypted sequentially. Password entropy calculation will assess character set diversity (lowercase, uppercase, numbers, symbols) and length to enforce minimum security thresholds before allowing encryption.