I'm working on an automated backup solution to protect my files on my Linux servers. However, I'm not sure about how to securely encrypt the resulting archives. I am using 64bit linux, and I am looking for a solution that would have a separate key/password for each individual archive backed up. 

I've seen solutions such as:

1. Using TrueCrypt to create a small container for the individual archive
2. Creating a luks?/dmcrypt volume and just putting everything in there

How would I do this where each backup copy would have its individual key/key files? I'm looking for a solution that where all of the private keys would not be exposed on the machine being backed up? [I.e. I have a key file, and it has a generated keyfile just for that backup]