Rob G. Jansen, PhD

Computer Scientist, Researcher, and Principal Investigator
U.S. Naval Research Laboratory, Washington, DC, USA

Publication Details

  1. Citation

    Akshaya Mani, T Wilson-Brown,  Rob JansenAaron Johnson, and Micah Sherr:
    Understanding Tor Usage with Privacy-Preserving Measurement. Internet Measurement Conference, 2018.

    Author Links

    Venue Links


    The Tor anonymity network is difficult to measure because, if not done carefully, measurements could risk the privacy (and potentially the safety) of the network’s users. Recent work has proposed the use of differential privacy and secure aggregation techniques to safely measure Tor, and preliminary proof-of-concept prototype tools have been developed in order to demonstrate the utility of these techniques. In this work, we significantly enhance two such tools—PrivCount and Private Set-Union Cardinality—in order to support the safe exploration of new types of Tor usage behavior that have never before been measured. Using the enhanced tools, we conduct a detailed measurement study of Tor covering three major aspects of Tor usage: how many users connect to Tor and from where do they connect, with which destinations do users most frequently communicate, and how many onion services exist and how are they used. Our findings include that Tor has ∼8 million daily users, a factor of four more than previously believed. We also find that ∼40% of the sites accessed over Tor have a domain name, ∼10% of the sites have an domain name, and ∼80% of the sites have a domain name that is included in the Alexa top 1 million sites list. Finally, we find that ∼90% of lookups for onion addresses are invalid, and more than 90% of attempted connections to onion services fail.


      title = {Understanding Tor Usage with Privacy-Preserving Measurement},
      author = {Mani, Akshaya and Wilson-Brown, T and Jansen, Rob and Johnson, Aaron and Sherr, Micah},
      booktitle = {Internet Measurement Conference},
      year = {2018},
      doi = {10.1145/3278532.3278549},