Boxcryptor is a software tool that provides end-to-end encryption for cloud storage services such as Dropbox, Google Drive, and OneDrive. It uses AES-256 and RSA encryption to secure files and folders. Boxcryptor also offers two-factor authentication, password policies, and the ability to share encrypted files securely with other users. Its key features include cross-platform compatibility, ease of use, and support for multiple cloud storage providers.