DDG have a tor hidden service for search [1] and so you can search annonamusly through that, even if someone has access to the ssl privet key.
[1] http://www.gabrielweinberg.com/blog/2010/08/duckduckgo-now-o...
[1] http://www.gabrielweinberg.com/blog/2010/08/duckduckgo-now-o...
I2P is similar to Tor, but encrypted AFAIK.
https://www.torproject.org/docs/hidden-services.html.en
EDIT: To be clear, I am saying that tor DOES provide end-to-end encryption, but only when you're using a tor hidden service -- which is also what the parent poster said.