How Difficult Should the Puzzles Be?


The censor can impersonate any relevant IP address with ease. 

Each puzzle yields a chunk of known proxies.

Time is on our side
100,000 forwarders (reasonable)
Bernoulli trials: 300,000 puzzles for about 50% of proxies
Each puzzle takes a week to solve: 1,400 compute-years to block 50% of proxies