encrypted backup

[Eric S. Johansson]

I need to back up a few systems to untrusted hosts.  So I would like to 
have the remote contents encrypted.  But because the remote host is 
untrusted, I can't do the encryption on the remote host.  I'm currently 
using http://rsnapshot.org/ for local backups (works very nice by the 
way) but the encryption issue is a very important one.

If I need to roll my own solution, what comes to mind is:

1) Building an copy of all my files via rsync, decrypting with gpg and 
then using rsnapshot to back up to the remote machine

2) using nbd/gnbd to create a local disk image and mounts it as an 
encrypted device.  (enbd is another possibility but remembering to 
rebuild the kernel every time there's an update is less than ideal.  I 
have a hard time remembering to do apt-get update on all my servers on a 
regular basis (topic drift: any way to automate this or at the very 
least triggered from one location?)

3)??

I'd really prefer an off the shelf, actively supported, solution if 
there is one available.

---eric