Remote encrypted backup solutions such as Carbonite rely on proprietary software both on the client and server side.

An open modular alternative sounds appealing. Providers such has geneticmail.com offer file hosting with webdav which should be a good and open backend.

!!! Modular approach with filesystem

[{GraphViz title='Encrypted backup3' filter='dot' imap='false'

node [shape=box];

$(nodeAttributes)
"Local Storage"--"Backup Program"
"Backup Program"--"Ecryptfs view of medium"
"Remote storage"--"Remote webdav server"
"Remote webdav server"--"Webdav mount"
"Ecryptfs view of medium"--"Webdav mount"

}]