Extrapolating network totals from hidden-service statistics

Abstract

Starting on December 19, 2014, we added two new statistics to the Tor software that shall give us some first insights into hidden-service usage. The first statistic is the number of cells on rendezvous circuits observed by a rendezvous point, and the second is the number of unique .onion addresses observed by a hidden-service directory. Each relay that opts in to reporting these statistics publishes these two numbers for 24-hour intervals of operation. In the following, we describe an approach for extrapolating network totals from these statistics. The goal is to learn what amount of traffic can be attributed to hidden-service usage and how many unique .onion addresses exist in the network. We show that we can extrapolate network totals with reasonable accuracy as long as at least 1% of relays report these statistics.