http://tttyx2vwp7ihml3vkhywwcizv6nbwrikpgeciy3qrow7l7muak2pnhad.onion/History.html
These were to be
combined with published public DH keys. Interestingly, this would
still yield perfect forward secrecy if the private DH keys of the
onion routers were rotated on, e.g., a daily basis. However, our
primary focus was on potential efficiency gains in computation rather
than this point.