I'm running Windows and strongly considering using Amazon S3 to back up some of my more important data, but i'm having trouble coming up with a good encryption strategy. I'm a fan of Truecypt and use it locally but it sounds incredibly inefficient to use over S3. For example, if I want to work on some photos that are in a 5GB container i'd have to download the entire container to mount it. Costly and impractical.
I've heard of Duplicity and it sounds like a good option, but i'd rather have a more elegant solution that doesn't involve cygwin. What are my options?