Growing businesses find that a server set-up provides more control over file management, sharing, back-up and security, plus efficiency when adding people.
This means the core features would need to be repackaged into light application or built from scratch to be accessible by mobile devices and could lead to multiple issues such as version control, file sharing, interfacing with the legacy application apart from security.
Each file will then be issued a unique, sophisticated decryption key which only the file holder will control, allowing them to share the file as they choose.