Come work with us!

I’m very pleased to announce that — along with George Danezis and Tomaso Aste, head of our Financial Computing group — I’ve been awarded a grant to continue our work on distributed ledgers (aka “blockchain-like things”) for the next three years.

Our group has already done a lot of research in this space, including George’s and my recent paper on centrally banked cryptocurrencies (at NDSS 2016) and Jens’ paper (along with Markulf Kohlweiss, a frequent UCL collaborator) on efficient ring signatures and applications to Zerocoin-style cryptocurrencies (at Eurocrypt 2015).  It’s great to have this opportunity to further investigate the challenges in this space and develop our vision for the future of these technologies, so big thanks to the EPSRC!

Anyway, the point of this post is to advertise, as part of this grant, three positions for postdoctoral researchers.  We are also seeking collaboration with any industrial partners investigating the potential usage of distributed ledgers, and in particular ones looking at the application of these ledgers across the following settings (or with a whole new setting in mind!):

  • Identity management. How can identities be stored, shared, and issued in a way that preserves privacy, prevents theft and fraud, and allows for informal forms of identity in places where no formal ones exist?
  • Supply chain transparency. How can supply chain information be stored in a way that proves integrity, preserves the privacy of individual actors, and can be presented to the end customer in a productive way?
  • Financial settlement. How can banking information be stored in a way that allows banks to easily perform gross settlement, reduces the burden on a central bank, and enables auditability of the proper functioning of the system?
  • Administration of benefits. How can benefits be administered to and used by disadvantaged populations in a way that preserves privacy, provides useful visibility into their spending, and protects against potential abuses of the system?

We expect the postdoctoral researchers to work with us and with each other on the many exciting problems in this space, which are spread across cryptography, computer and network security, behavioural economics, distributed systems, usable security, human-computer interaction, and software engineering (just to name a few!).  I encourage anyone interested to reach out to me (Sarah) to discuss this further, whether or not they’ve already done research on the particular topic of distributed ledgers.

That’s all for now, but please get in touch with me if you have any questions, and in the years to come I hope to invite many people to come work with us in London and to announce the various outcomes of this exciting project!

Bitcoin workshop at Financial Crypto 2016

On 26 February 2016 the 3rd workshop on Bitcoin and Blockchain Research in association with Financial Cryptography 2016 took place in Barbados. This workshop aims to bring together researchers interested in cryptocurrencies to present their latest work and discuss together the future of Bitcoin. The program chairs were Sarah Meiklejohn from University College London and Jeremy Clark from Concordia University. The themes addressed during the workshop included blockchain architecture, anonymity, and proof of work alternatives. This event was also a great way for researchers with similar interests to network and share their ideas.

The workshop consisted of 2 keynotes and 4 plenary sessions: Bitcoin network analysis, Enhancing Bitcoin, Ethereum, and Blockchain Architecture.

Nathaniel Popper kicked off the day with a keynote presentation. Nathaniel is a journalist from the New York Times and author of the book ‘Digital Gold: The Untold story of Bitcoin’. He went on to speak about the history of Bitcoin covering Silk Road, Mt Gox, as well as the role of governments.

Then the first session, about Bitcoin network analysis, included two talks. The first one, Stressing Out: Bitcoin Stress Testing, by Khaled Baqer et al., was about DoS attack on Bitcoin, and was presented by Ross Anderson due to visa issues. The second one was Why buy when you can rent? Bribery attacks on Bitcoin-style consensus, by Joseph Bonneau on bribery attacks and cloud mining.

The next session, Enhancing Bitcoin, started with a talk by Ethan Heilman, Blindly Signed Contracts: Anonymous On-Blockchain and Off-Blockchain Bitcoin Transactions, on how to enhance Bitcoin anonymity. Then Mathieu Turuani gave a talk on Automated Verification of Electrum wallet, followed by Aggelos Kiayias on Proof of Proof of Work. Today many light-weight clients use SPV verification instead of full verification. Is it possible to have an even lighter verification? They introduce a modification of the Bitcoin blockchain protocol with sublinear complexity in the length of the chain.

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Our contributions to the UK Distributed Ledger Technology report

The UK Government Office for Science, has published its report on “Distributed ledger technology: beyond block chain” to which UCL’s Sarah Meiklejohn, Angela Sasse and myself (George Danezis) contributed parts of the security and privacy material. The review, looks largely at economic, innovation and social aspects of these technologies. Our part discusses potential threats to ledgers, as well as opportunities to build robust security systems using ledgers (Certificate Transparency & CONIKS), and overcome privacy challenges, including a mention of the technology.

You can listen to the podcast interview Sarah gave on the report’s use cases, recommendations, but also more broadly future research directions for distributed ledgers, such as better privacy protection.

In terms of recommendation, I personally welcome the call for the Government Digital Services, and other innovation bodies to building capacity around distributed ledger technologies. The call for more research for efficient and secure ledgers (and the specific mention of cryptography research) is also a good idea, and an obvious need. When it comes to the specific security and privacy recommendation, it simply calls for standards to be established and followed. Sadly this is mildly vague: a standards based approach to designing secure and privacy-friendly systems has not led to major successes. Instead openness in the design, a clear focus on key end-to-end security properties, and the involvement of a wide community of experts might be more productive (and less susceptible to subversion).

The report is well timed: our paper on “Centrally Banked Crypto-Currencies” will be presented in February at a leading security conference, NDSS 2016, by Sarah Meiklejohn, largely inspired by the research agenda published by the Bank of England. It provides some answers to the problems of scalability and eco-friendliness of current proof-of-work based ledger design.

Sarah Meiklejohn – Security and Cryptography

Sarah Meiklejohn As a child, Sarah Meiklejohn thought she might become a linguist, largely because she was so strongly interested in the work being done to decode the ancient Greek writing systems Linear A and Linear B.

“I loved all that stuff,” she says. “And then I started doing mathematics.” At that point, with the help of Simon Singh’s The Code Book, she realised the attraction was codebreaking rather than human languages themselves. Simultaneously, security and privacy were increasingly in the spotlight.

“I’m a very private person, and so privacy is near and dear to my heart,” she says. “It’s an important right that a lot of people don’t seem interested in exercising, but it’s still a right. Even if no one voted we would still agree that it was important for people to be able to vote.”

It was during her undergraduate years at Brown, which included a fifth-year Masters degree, that she made the transition from mathematics to cryptography and began studying computer science. She went on to do her PhD at the University of California at San Diego. Her appointment at UCL, which is shared between the Department of Computer Science and the Department of Crime Science, is her first job.

Probably her best-known work is A Fistful of Bitcoins: Characterizing Payments Among Men with No Names (PDF), written with Marjori Pomarole, Grant Jordan, Kirill Levchenko, Damon McCoy, Geoffrey M. Voelker, and Stefan Savage and presented at USENIX 2013, which studied the question of how much anonymity bitcoin really provides.

“The main thing I was trying to focus on in that paper is what bitcoin is used for,” she says. The work began with buying some bitcoin (in 2012, at about £3 each), and performing some transactions with them over a period of months. Using the data collected this way allowed her to uncover some “ground truth” data.

“We developed these clustering techniques to get down to single users and owners.” The result was that they could identify which addresses belonged to which exchanges and enabled them to get a view of what was going on in the network. “So we could say this many bitcoins passed through this exchange per month, or how many were going to underground services like Silk Road.”

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