  Astroturfing, i.e., the fabrication of public discourse by private or
state-controlled sponsors via the creation of fake online accounts, has become
incredibly widespread in recent years. It gives a disproportionally strong
voice to wealthy and technology-savvy actors, permits targeted attacks on
public forums and could in the long run harm the trust users have in the
internet as a communication platform. Countering these efforts without
deanonymising the participants has not yet proven effective; however, we can
raise the cost of astroturfing. Following the principle `one person, one
voice', we introduce Trollthrottle, a protocol that limits the number of
comments a single person can post on participating websites. Using direct
anonymous attestation and a public ledger, the user is free to choose any
nickname, but the number of comments is aggregated over all posts on all
websites, no matter which nickname was used. We demonstrate the deployability
of Trollthrottle by retrofitting it to the popular news aggregator website
Reddit and by evaluating the cost of deployment for the scenario of a national
newspaper (168k comments per day), an international newspaper (268k c/d) and
Reddit itself (4.9M c/d).
