Diversity is our strength

On Friday evening, US President Donald Trump signed an executive order suspending visas to citizens of seven countries for at least 90 days. Among the many other implications of this ban — none of which we want to minimise with our focus on the implications for academics — this now implies that (1) students who are citizens (even dual citizens) of these countries are now unable to study in the US or attend conferences there, and (2) academics who are citizens of these countries and who legally work and live in the US are now unable to leave (to, say, attend conferences or visit another academic institution), as they would not be allowed back in.

We receive many inquiries each year from strong applicants from these seven countries, and according to a statement issued by many US-based academics, more than 3,000 Iranian students received PhDs from American universities in the past 3 years. Across our nine faculty members, we currently have funding available for numerous PhD students and postdoctoral researchers. If any student is stranded outside of the US, we of course hope that they are able to make it back quickly, but have funding for internships that would allow them to work from here in the interim. In organising conferences, we and our wider UCL colleagues are doing all we can to organise them in places without such bans in place, and where that is not possible to enable remote participation.

Most of all, as a group that prides itself on the quality and openness of its research and on its international reach, we would like to re-affirm our commitment to working with the best possible students and academics, regardless of their religion or their country of origin (or indeed anything aside from their scientific contributions). To quote a statement from the International Association of Cryptologic Research (IACR), “the open exchange of ideas requires freedom of movement.” To address the full effects of this ban we of course need far more international cooperation, but we hope that even our small actions can help mitigate the damage that has already been done to our friends and colleagues, both within and outside of the US, and that promises to continue to be done in the future.

Nicolas Courtois
Emiliano de Cristofaro
George Danezis
Jens Groth
Sarah Meiklejohn
Steven Murdoch
David Pym
Angela Sasse
Gianluca Stringhini

Smart contracts beyond the age of innocence

Why have Bitcoin, with its distributed consistent ledger, and now Ethereum with its support for fully fledged “smart contracts,” captured the imagination of so many people, both within and beyond the tech industry? The promise to replace obscure stores of information and arcane contract rules – with their inefficient, ambiguous, and primitive human interpretations – with publicly visible decentralized ledgers reflects the growing technological zeitgeist in their guarantee that all participants would know and be able to foresee the consequences of both their own actions and the actions of all others. The precise specification of contracts as code, with clauses automatically executed depending on certain sets of events and permissible user actions, represents for some a true state of utopia.

Regardless of one’s views on the potential for distributed ledgers, one of the most notable innovations that smart contracts have enabled thus far is the idea of a DAO (Decentralized Autonomous Organization), which is a specific type of investment contract, by which members individually contribute value that then gets collectively invested under some governance model.  In truly transparent fashion, the details of this governance model, including who can vote and how many votes are required for a successful proposal, are all encoded in a smart contract that is published (and thus globally visible) on the distributed ledger.

Today, this vision met a serious stumbling block: a “bug” in the contract of the first majorly successful DAO (which broke records by raising 11 million ether, the equivalent of 150 million USD, in its first two weeks of operation) allowed third parties to start draining its funds, and to eventually make off with 4% of all ether. The immediate response of the Ethereum and DAO community was to suspend activity – seemingly an anathema for a ledger designed to provide high resiliency and availability – and propose two potential solutions: a “soft-fork” that would impose additional rules on miners in order to exclude all future transactions that try to use the stolen ether, or, more drastically (and running directly contrary to the immutability of the ledger),  a “hard-fork” that would roll back the transactions in which the attack took place, in addition to the many legitimate transactions that took place concurrently.  Interestingly, a variant of the bug that enabled the hack was known to and dismissed by the creators of the DAO (and the wider Ethereum community).

While some may be surprised by this series of events, Maurice Wilkes, designer of the EDSAC, one of the first computers, reflected that “[…] the realization came over me with full force that a good part of the remainder of my life was going to be spent in finding errors in my own programs.” It is not the case that because a program is precisely defined it is easy to foresee what it will do once executed on its own under the control of users.  In fact, Rice’s theorem explicitly states that it is not possible in general to show that the result of programs, and thus smart contracts, will have any specific non-trivial property.

This forms the basis on which modern verification techniques operate: they try to define subsets of programs for which it is possible to prove some properties (e.g., through typing), or attempt to prove properties in a post-hoc way (e.g., through verification), but under the understanding that they may fail in general.  There is thus no scientific basis on which one can assert generally that smart contracts can easily provide clarity into and foresight of their consequences.

The unfolding story of the DAO and its consequences for the Ethereum community offers two interesting insights. First, as a sign that the field is maturing, there is an explicit call for understanding the computational space of safe contracts, and contracts with foreseeable consequences. Second, it suggests the need for smart contracts protecting significant assets to include external, possibly social, mechanisms in order to unlock significant value transfers. The willingness of exchanges to suspend trading and of the Ethereum developers to suggest a hard-fork is a last-resort example of such a social mechanism. Thus, politics – the discipline of collective management – reasserts itself as having primacy over human affairs.

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!

Teaching cybersecurity to criminologists

I recently had the pleasure of teaching my first module at UCL, an introduction to cybersecurity for students in the SECReT doctoral training centre.

The module had been taught before, but always from a fairly computer-science-heavy perspective. Given that the students had largely no background in computer science, and that my joint appointment in the Department of Security and Crime Science has given me at least some small insight into what aspects of cybersecurity criminologists might find interesting, I chose to design the lecture material largely from scratch. I tried to balance the technical components of cybersecurity that I felt everyone needed to know (which, perhaps unsurprisingly, included a fair amount of cryptography) with high-level design principles and the overarching question of how we define security. Although I say I designed the curriculum from scratch, I of course ended up borrowing heavily from others, most notably from the lecture and exam material of my former supervisor’s undergraduate cybersecurity module (thanks, Stefan!) and from George’s lecture material for Introduction to Computer Security. If anyone’s curious, the lecture material is available on my website.

As I said, the students in the Crime Science department (and in particular the ones taking this module) had little to no background in computer science.  Instead, they had a diverse set of academic backgrounds: psychology, political science, forensics, etc. One of the students’ proposed dissertation titles was “Using gold nanoparticles on metal oxide semiconducting gas sensors to increase sensitivity when detecting illicit materials, such as explosives,” so it’s an understatement to say that we were approaching cybersecurity from different directions!

With that in mind, one of the first things I did in my first lecture was to take a poll on who was familiar with certain concepts (e.g., SSH, malware, the structure of the Internet), and what people were interested in learning about (e.g., digital forensics, cryptanalysis, anonymity). I don’t know what I was expecting, but the responses really blew me away! The students overwhelmingly wanted to hear about how to secure themselves on the Internet, both in terms of personal security habits (e.g., using browser extensions) and in terms of understanding what and how things might go wrong. Almost the whole class specifically requested Tor, and a few had even used it before.

This theme of being (pleasantly!) surprised continued throughout the term.  When I taught certificates, the students asked not for more details on how they work, but if there was a body responsible for governing certificate authorities and if it was possible to sue them if they misbehave. When I taught authentication, we played a Scattergories-style game to weigh the pros and cons of various authentication mechanisms, and they came up with answers like “a con of backup security questions is that they reveal cultural trends that may then be used to reveal age, ethnicity, gender, etc.”

There’s still a month and a half left until the students take the exam, so it’s too soon to say how effective it was at teaching them cybersecurity, but for me the experience was a clear success and one that I look forward to repeating and refining in the future.