http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/proposals/344-protocol-info-leaks.html
This attack, and path bias attacks that are used in the next two sections, do
have some minor engineering barriers when being performed against both onion
and exit traffic, because the onion service traffic is restricted to
particular hops in the case of HSDIR and intro point circuits.