I assume you're talking about using HiDrive and Boxcryptor on Windows. Boxcryptor for Windows itself does not transfer any files to or from HiDrive. In order to use Boxcryptor with HiDrive you have to integrate HiDrive into the file system of your operating system - e.g. by mounting it via WebDAV or SMB/CIFS as a network drive. When HiDrive is present in your operating system, Boxcryptor can use it as a location to store files. The actual file transfer is then done by Windows (or another software) which provides the network drive mount.
PS: Instead of directly using the HiDrive network drive as a Boxcryptor location, you could store the encrypted files in a local folder on your harddisk and use rsync to synchronize this folder with HiDrive.