http://rzuwtppveur6yh3n2in7trmddgrkuhww4eb2znykgjwubihfpljiyuid.onion
So, what should we do?
Suppose the attacker controls, or can observe, C relays.
Suppose there are N relays total.
If you select new entry and exit relays each time you use the network, the attacker will be able to correlate all traffic you send with probability around (c/n)^2.