Enhanced HKDF-based key derivation with improved security features

- Implemented proper RFC 5869 compliant HKDF key derivation process
- Added Perfect Forward Secrecy (PFS) key for enhanced session security
- Improved key separation using unique info parameters for each derived key
- Enhanced salt size from 32 to 64 bytes for increased entropy
- Added comprehensive key validation and error handling
- Implemented proper ECDH + HKDF integration following Web Crypto API best practices
- Added metadata encryption key for enhanced data protection
- Improved compatibility with modern cryptographic standards (RFC 7748, NIST SP 800-56A)
 -Enhanced logging and debugging capabilities for cryptographic operations
- Maintained backward compatibility while upgrading security infrastructure
Security improvements:
- Cryptographic isolation between different key purposes
- Enhanced protection against cross-key attacks
- Improved resistance to future key compromise scenarios
- Better compliance with OWASP cryptographic storage guidelines
Technical details:
- Refactored deriveSharedKeys() method for proper HKDF implementation
- Updated WebRTC manager to use new messageKey API
- Added comprehensive error handling and validation
- Improved browser compatibility with standardized cryptographic operations
- This update strengthens the existing security foundation with modern cryptographic practices while maintaining full system compatibility.

sw.js

@@ -1,9 +1,9 @@
 // SecureBit.chat Service Worker
-// Conservative PWA Edition v4.4.18 - Minimal Caching Strategy
+// Conservative PWA Edition v4.4.99 - Minimal Caching Strategy
 
-const CACHE_NAME = 'securebit-pwa-v4.4.18';
-const STATIC_CACHE = 'securebit-pwa-static-v4.4.18';
-const DYNAMIC_CACHE = 'securebit-pwa-dynamic-v4.4.18';
+const CACHE_NAME = 'securebit-pwa-v4.4.99';
+const STATIC_CACHE = 'securebit-pwa-static-v4.4.99';
+const DYNAMIC_CACHE = 'securebit-pwa-dynamic-v4.4.99';
 
 // Essential files for PWA offline functionality
 const STATIC_ASSETS = [