Currently I'm using EncFS to encrypt my directory "confidential" to ".encconfidential" and sync that encrypted directory using an online service (e.g. Dropbox, UbuntuOne etc). However my entire disk is already LUKS encrypted, so the double encryption takes a toll on performance.
I wonder is there an "inverted" EncFS option? An unencrypted directory gets mounted and in the mounted directory you only see encrypted files. So I could work with the unencrypted documents while the sync tool sees and read/writes the encrypted files only.
Clarification: My primary use case is sync not backup. I want to be able to securely keep machines in sync without the double encryption penalty when operating local (I have to wait when I hit save, compared to transmission time an encrypted operation is a minimal increment in time - and it is background time, not user time)