[Noisebridge-discuss] Client-side secure equivalents of Dropbox et al?

[Sai]

I'd like something that does what Dropbox does - i.e. transparent
synch, backup w/ versioning, etc - but
a) does full crypto at the client side (inaccessible to the server),
so that the data can't be stolen, monitored, taken by warrant on the
server, etc
b) puts the data in an S3 or scp account of my own choice (not the
service's), so I directly pay the actual cost and no data even gets
sent to a SAAS provider

The closest I'm aware of that does this are:
http://www.tarsnap.com
https://spideroak.com

Do y'all know of better?

- Sai