Client-side encryption before the desktop backup software ships my data off to the cloud

Question

I have a good price and fast upload with a local online back-up provider. I like their service and only really have one complaint: they don’t encrypt my data client-side before transmitting it to their services.

Is there a good way, on the Mac, to encrypt my files before they are uploaded to the back-up provider? My data set is quite large, so copying all the files into a second encrypted location (encrypted disk image or similar) is impractical.

The back-up provider monitors the folders I have specified as back-up folders, and transmit any file changes in them.

Answer 1

encfs now works for Mac: http://en.wikipedia.org/wiki/EncFS

There are two solutions:

1) Backup service <-> Stored encrypted files <-> EncFS <-> Mounted transparent files <-> User

You have your files encrypted on the disk, in the folders you specify as back-up folders, and when you work with your files their unencrypted version will be mounted in another folder once you type the password.

That protects you against physical theft, too.

2) Backup service <-> Mounted encrypted files <-> EncFS <-> Stored transparent files <-> User

You have your files unencrypted on the disk, and you work on the folders where you files actually are stored. You use encfs --reverse to mount their encrypted version in a folder which you will tag as back-up folders.

You have faster access to your files, but this back-up software needs to be polite enough to wait until you acutally mount the encrypted folder before it starts uploading/downloading any changes.

Answer 2

It turns out Carbonite optimally works this way but only under Windows. Their Mac client does only allow to have managed certificates, which means they stay in control of the files.