客户端文件加密工具

使用 HTML5、CSS3 和 JavaScript（配合 Web Crypto API）创建一个客户端文件加密工具。构建支持拖放操作的文件选择界面，并配备进度指示器。实现基于密码的安全密钥派生（PBKDF2）的 AES-256-GCM 加密。添加对同时加密多个文件的支持，采用批处理方式。包含密码强度强制策略，并通过熵值计算评估密码强度。生成可下载的加密文件，并支持自定义文件扩展名。创建解密界面，并验证用户输入的密码。实现安全的内存管理机制，自动清除敏感数据。添加详细的加密操作日志，且不存储任何敏感信息。支持加密密钥的导出与导入，并附带适当的安全警告。支持大文件的流式加密与分块处理。

Create a client-side file encryption tool using HTML5, CSS3, and JavaScript with the Web Crypto API. Build a drag-and-drop interface for file selection with progress indicators. Implement AES-256-GCM encryption with secure key derivation from passwords (PBKDF2). Add support for encrypting multiple files simultaneously with batch processing. Include password strength enforcement with entropy calculation. Generate downloadable encrypted files with custom file extension. Create a decryption interface with password verification. Implement secure memory handling with automatic clearing of sensitive data. Add detailed logs of encryption operations without storing sensitive information. Include export/import of encryption keys with proper security warnings. Support for large files using streaming encryption and chunked processing.