I'm a Systems Engineer focusing on security and encryption while building a better Internet at CloudFlare. Prior to joining CloudFlare, I did a PhD in Computer Science in the Security Group at Princeton University, which is an important part of Computer Science history. My dissertation on Accountable Algorithms was advised by Edward W. Felten and supported by the Center for Information Technology Policy where I studied many topics in security, privacy, and how technology informs policy decisions. For a time, I was also advised by Andrew Appel and worked on memory safety and software security.

The following facts about me may or may not interest you: I received the National Science Foundation Graduate Research Fellowship in 2011. For many years, I traveled to Boston each fall to perform Improbable feats of engineering. I got married to my secret high-school crush in 2012.

Deeper in the past, I attended a small college near Boston, MA where I spent a lot of time playing with technology and making it accessible to the masses. Prior to that, I grew up in Monterey, CA where I can recommend a good dentist. It was there that I got my start as a Computer Scientist, and experienced the inner workings of government.

I don't always blog, but when I do, you can find my ramblings linked from the publications page. You might also find me making birdcalls online from time to time.


I'm interested in a broad swath of topics in and outside of security (computer and otherwise), privacy (online and otherwise), and related questions in public policy. I'm also strongly interested in cryptography. My dissertation research was on Accountable Algorithms, and tools for bridging technical assurances with human oversight.

For more information, you should contact me.

Peer-reviewed Publications

  • Bonneau, J., Miller, A., Clark, J., Narayanan, A., Kroll, J., and Felten, E., "SoK: Bitcoin and second-generation cryptocurrencies", 36th IEEE Symposium on Security and Privacy, San Jose, CA, May 18-20 [PDF]
  • Kroll, J., Felten, E., and Haldermann, J. A., "Efficiently Auditing Multi-Level Elections", 6th International Conference on Electronic Voting (EVOTE 2014), Lochau, Austria, October 28-31, 2014 [PDF]
  • Edmundsen, A., Simpson, A.K., Kroll, J., and Felten, E., "Security Audit of Safeplug 'Tor in a Box'", 4th USENIX Workshop on Free and Open Communication on the Internet (FOCI 2014), San Diego, CA, August 18, 2014.[PDF]
  • Clark, J., Bonneau, J., Felten, E., Kroll, J., Miller, A., and Narayanan, A., "On Decentralizing Prediction Markets and Order Books", Thirteenth Workshop on the Econpmics of Information Security (WEIS 2014), State College, PA, June 23-24 2014. [PDF]
  • Kroll, J., Stewart, J., and Appel, A. "Portable Software Fault Isolation". Computer Security Foundations, 2014 (CSF 2014), Vienna, Austria, July 19-22 2014. [PDF]
  • Kroll, J., Felten, E., and Boneh, D. "Secure Protocols for Accountable Warrant Execution". Preprint. [PDF]
  • Goldfeder, S., Bonneau, J., Felten, E., Narayanan, A., "Securing Bitcoin Wallets with Threshhold Signatures". Preprint. [PDF]
  • Bonneau, J., Narayanan, A., Miller, A., Clark, J., and Kroll, J. "Mixcoin: Anonymity for Bitcoin with accountable mixes," Financial Cryptography, 2014 (FC 2014), Bridgetown, Barbados, March 3-7 2014. [PDF (full version)]
  • Kroll, J., Davey, I., and Felten, E., "The Economics of Bitcoin Mining, or Bitcoin in the Presence of Adversaries", The Twelfth Workshop on the Economics of Information Security (WEIS 2013), Washington, DC, June 10-11 2013. [PDF]
  • Kroll, J. and D. Dean, “BakerSFIeld: Bringing Software Fault Isolation to the x64,” SRI Computer Science Laboratory Technical Report, 2009. [PDF]
  • Martell, C. and J. Kroll, “Corpus-Based Gesture Analysis: An extension of the FORM dataset for the automatic detection of phases in a gesture”, Int. J. Semantic Computing, 1(4): 521-536 (2007). [PDF] [Journal Page]
  • Martell, C. and J. Kroll, “Using FORM to Predict Phase Labels”, Proceedings of the Language Resources and Evaluation Conference, Workshop on Multimodal Corpora, Genoa, Italy, 27 May 2006. [PDF]


Public Policy Publications and Regulatory Filings

  • Barocas, S., Felten, E., Huey, J., Kroll, J., and Narayanan, A. "Big Data and Consumer Privacy in the Internet Economy". Comment to the NTIA Big Data Request for Comments, 79 Fed. Reg. 32714. August 5, 2014. [PDF]

Other Publications

  • Law Review Articles

    • Kroll, J. A., Huey, J., Baroas, S., Felten, E. W., Reidenberg, J. R., Robinson, D. G., and Yu, H. "Accountable Algorithms" University of Pennsylvania Law Review, Vol. 165, 2017 Forthcoming. [PDF (draft)]
  • Popular Articles

    • Felten, E., and Kroll, J. "Heartbleed Shows Government Must Lead on Internet Security". Scientific American, 16 April 2014. [article]
    • Kroll, J. "The Cyber Conundrum". The American Prospect. 1 June 2015. [article]
    • Kroll, J. "The Cyber Conundrum: A Security Update". The American Prospect Online. 3 June 2015. [article]
  • Blog Posts


    • Kroll, J. Powell, A. and Vis, F., "Algorithmic Accountability". Big Boulder Conference, June 24, 2016. (Invited) [event]
    • Kroll, J. "Accountable Algorithms". "Unlocking the Black Box" Conference, Internet & Society Project, Yale Law School, 1 April 2016. (Competitive Selection) [event]
    • Kroll, J. "Accountable Algorithms". "Algorithmic Power and Accountability in Black-Box Platforms" Workshop, Media Policy Project, London School of Economics, 25 January 2016. (Invited) [event]
    • Kroll, J. "Big Data, Fairness, and Nondiscrimination". New Jersey Attorney General's Advocacy Institue In-Service Training, August 7, 2014.
    • Kroll, J. "Accountable Algorithms". Princeton Joint ACM/IEEE Computer Society Chapters Meeting, 17 April 2014 [event]
    • Kroll, J. "The Economics of Bitcoin Mining, or Bitcoin in the Presence of Adversaries". Princeton University Center for Information Technology Policy Luncheon Series, 14 November 2013 [event] [video]
    • Barber, G. and Kroll, J. "Drones: Not Just for Military Use". New Jersey Attorney General's Advocacy Institute In-Service Training, August 8, 2013 (CLE credit course).
    • Felten, E. and Kroll, J. "The State of Electronic Voting". Princeton University Center for Information Technology Policy Luncheon Series, 18 October 2012. [event] [video]
    • Kroll, J. "Seeing Under Sea: Applications of Computer Vision in Underwater Video," Plenary Address, Harvard Undergraduate Research Symposium, Nov. 2006 (Accepted by faculty review; top 3 of 140 papers).



I sincerely enjoy teaching and am always looking for chances to do more of it. I've been fortunate to have many opportunities to be a teacher, a tutor, a docent, a guest speaker, and many other things. Please contact me if you'd like to know more.

I have taught the following university-level courses:

  • Princeton University, Department of Computer Science. Assistant in Instruction, Computer Science 226: Algorithms and Data Structures. Professor Robert Sedgewick, Instructor. Spring 2011.
  • Princeton University, Department of Computer Science. Assistant in Instruction, Computer Science 432: Information Security. Professor Edward Felten, Instructor. Fall 2010.
  • Harvard University, Department of Mathematics. Head Course Assistant (of 6), Mathematics 23a/b: Linear Algebra and Real Analysis I/II. Dr. Paul G. Bamberg, Instructor. 2006-2007.

Please contact me if you have a specific interest and we can talk.


My curriculum vitae. I cannot guarantee that the one on this website is up-to-date.

For a current copy of my CV, it would be best to contact me.

Contact Me

I am most easily contacted via E-mail at .

If you prefer to send mail of the physical variety, please send it to my employer:

Joshua Kroll
CloudFlare, Inc
101 Townsend St.
San Francisco, CA 94107