Coconut E-Petition Implementation

An interesting new multi-authority selective-disclosure credential scheme called Coconut has been recently released, which has the potential to enable applications that were not possible before. Selective-disclosure credential systems allow issuance of a credential (having one or more attributes) to a user, with the ability to unlinkably reveal or “show” said credential at a later instance, for purposes of authentication or authorization. The system also provides the user with the ability to “show” specific attributes of that credential or a specific function of the attributes embedded in the credential; e.g. if the user gets issued an identification credential and it has an attribute x representing their age, let’s say x = 25, they can show that f(x) > 21 without revealing x.

High-level overview of Coconut, from the Coconut paper

A particular use-case for this scheme is to create a privacy-preserving e-petition system. There are a number of anonymous electronic petition systems that are currently being developed but all lack important security properties: (i) unlinkability – the ability to break the link between users and specific petitions they signed, and (ii) multi-authority – the absence of a single trusted third party in the system. Through multi-authority selective disclosure credentials like Coconut, these systems can achieve unlinkability without relying on a single trusted third party. For example, if there are 100 eligible users with a valid credential, and there are a total of 75 signatures when the petition closes, it is not possible to know which 75 people of the total 100 actually signed the petition.

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UK Faster Payment System Prompts Changes to Fraud Regulation

Banking transactions are rapidly moving online, offering convenience to customers and allowing banks to close branches and re-focus on marketing more profitable financial products. At the same time, new payment methods, like the UK’s Faster Payment System, make transactions irrevocable within hours, not days, and so let recipients make use of funds immediately.

However, these changes have also created a new opportunity for fraud schemes that trick victims into performing a transaction under false pretences. For example, a criminal might call a bank customer, tell them that their account has been compromised, and help them to transfer money to a supposedly safe account that is actually under the criminal’s control. Losses in the UK from this type of fraud were £145.4 million during the first half of 2018 but importantly for the public, such frauds fall outside of existing consumer protection rules, leaving the customer liable for sometimes life-changing amounts.

The human cost behind this epidemic has persuaded regulators to do more to protect customers and create incentives for banks to do a better job at preventing the fraud. These measures are coming sooner than UK Finance – the trade association for UK based banking payments and cards businesses – would like, but during questioning by the House of Commons Treasury Committee, their Chief Executive conceded that change is coming. They now focus on who will reimburse customers who have been defrauded through no fault of their own. Who picks up the bill will depend not just on how good fraud prevention measures are, but how effectively banks can demonstrate this fact.

UK Faster Payment Creates an Opportunity for Social Engineering Attacks

One factor that contributed to the new type of fraud is that online interactions lack the usual cues that help customers tell whether a bank is genuine. Criminals use sophisticated social engineering attacks that create a sense of urgency, combined with information gathered about the customer through illicit means, to convince even diligent victims that it could only be their own bank calling. These techniques, combined with the newly irrevocable payment system, create an ideal situation for criminals.

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What We Disclose When We Choose Not To Disclose: Privacy Unraveling Around Explicit HIV Disclosure Fields

For many gay and bisexual men, mobile dating or “hook-up” apps are a regular and important part of their lives. Many of these apps now ask users for HIV status information to create a more open dialogue around sexual health, to reduce the spread of the virus, and to help fight HIV related stigma. Yet, if a user wants to keep their HIV status private from other app users, this can be more challenging than one might first imagine. While most apps provide users with the choice to keep their status undisclosed with some form of “prefer not to say” option, our recent study which we describe in a paper being presented today at the ACM Conference on Computer-Supported Cooperative Work and Social Computing 2018, finds privacy may “unravel” around users who choose this non-disclosure option, which could limit disclosure choice.

Privacy unraveling is a theory developed by Peppet in which he suggests people will self-disclose their personal information when it is easy to do so, low-cost, and personally beneficial. Privacy may then unravel around those who keep their information undisclosed, as they are assumed to be “hiding” undesirable information, and are stigmatised and penalised as a consequence.

In our study, we explored the online views of Grindr users and found concerns over assumptions developing around HIV non-disclosures. For users who believe themselves to be HIV negative, the personal benefits of disclosing are high and the social costs low. In contrast, for HIV positive users, the personal benefits of disclosing are low, whilst the costs are high due to the stigma that HIV still attracts. As a result, people may assume that those not disclosing possess the low gain, high cost status, and are therefore HIV positive.

We developed a series of conceptual designs that utilise Peppet’s proposed limits to privacy unraveling. One of these designs is intended to artificially increase the cost of disclosing an HIV negative status. We suggest time and financial as two resources that could be used to artificially increase disclosure cost. For example, users reporting to be HIV negative could be asked to watch an educational awareness video on HIV prior to disclosing (time), or only those users who had a premium subscription could be permitted to disclose their status (financial). An alternative (or in parallel) approach is to reduce the high cost of disclosing an HIV positive status by designing in mechanisms to reduce social stigma around the condition. For example, all users could be offered the option to sign up to “living stigma-free” which could also appear on their profile to signal others of their pledge.

Another design approach is to create uncertainty over whether users are aware of their own status. We suggest profiles disclosing an HIV negative status for more than 6 months be switched automatically to undisclosed unless they report a recent HIV test. This could act as a testing reminder, as well as increasing uncertainty over the reason for non-disclosures. We also suggest increasing uncertainty or ambiguity around HIV status disclosure fields by clustering undisclosed fields together. This may create uncertainty around the particular field the user is concerned about disclosing. Finally, design could be used to cultivate norms around non-disclosures. For example, HIV status disclosure could be limited to HIV positive users, with non-disclosures then assumed to be a HIV negative status, rather than HIV positive status.

In our paper, we discuss some of the potential benefits and pitfalls of implementing Peppet’s proposed limits in design, and suggest further work needed to better understand the impact privacy unraveling could have in online social environments like these. We explore ways our community could contribute to building systems that reduce its effect in order to promote disclosure choice around this type of sensitive information.

 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 675730.

Can Ethics Help Restore Internet Freedom and Safety?

Internet services are suffering from various maladies ranging from algorithmic bias to misinformation and online propaganda. Could computer ethics be a remedy? Mozilla’s head Mitchell Baker warns that computer science education without ethics will lead the next generation of technologists to inherit the ethical blind spots of those currently in charge. A number of leaders in the tech industry have lent their support to Mozilla’s Responsible Computer Science Challenge initiative to integrate ethics with undergraduate computer science training. There is a heightened interest in the concept of ethical by design, the idea of baking ethical principles and human values into the software development process from design to deployment.

Ethical education and awareness are important, and there exist a number of useful relevant resources. Most computer science practitioners refer to the codes of ethics and conduct provided by the field’s professional bodies such as the Association for Computing Machinery and the Institute of Electrical and Electronics Engineers, and in the UK the British Computing Society and the Institute of Engineering and Technology. Computer science research is predominantly guided by the principles laid out in the Menlo Report.

But aspirations and reality often diverge, and ethical codes do not directly translate to ethical practice. Or the ethical practices of about five companies to be precise. The concentration of power among a small number of big companies means that their practices define the online experience of the majority of Internet users. I showed this amplified power in my study on the Web’s differential treatment of the users of Tor anonymity network.

Ethical code alone is not enough and needs to be complemented by suitable enforcement and reinforcement. So who will do the job? Currently, for the most part, companies themselves are the judge and jury in how their practices are regulated. This is not a great idea. The obvious misalignment of incentives is aptly captured in an Urdu proverb that means: “The horse and grass can never be friends”. Self-regulation by companies can result in inconsistent and potentially biased regulation patterns, and/or over-regulation to stay legally safe.

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When Convenience Creates Risk: Taking a Deeper Look at Security Code AutoFill on iOS 12 and macOS Mojave

A flaw in Apple’s Security Code AutoFill feature can affect a wide range of services, from online banking to instant messaging.

In June 2018, we reported a problem in the iOS 12 beta. In the previous post, we discussed the associated risks the problem creates for transaction authentication technology used in online banking and elsewhere. We described the underlying issue and that the risk will carry over to macOS Mojave. Since our initial reports, Apple has modified the Security Code AutoFill feature, but the problem is not yet solved.

In this blog post, we publish the results of our extended analysis and demonstrate that the changes made by Apple mitigated one symptom of the problem, but did not address the cause. Security Code AutoFill could leave Apple users in a vulnerable position after upgrading to iOS 12 and macOS Mojave, exposing them to risks beyond the scope of our initial reports.

We describe four example attacks that are intended to demonstrate the risks stemming from the flawed Security Code AutoFill, but intentionally omit the detail necessary to execute them against live systems. Note that supporting screenshots and videos in this article may identify companies whose services we’ve used to test our attacks. We do not infer that those companies’ systems would be affected any more or any less than their competitors.

Flaws in Security Code AutoFill

The Security Code AutoFill feature extracts short security codes (e.g., a one-time password or OTP) from an incoming SMS and allows the user to autofill that code into a web form, webpage, or app when authenticating. This feature is meant to provide convenience, as the user no longer needs to memorize and re-enter a code in order to authenticate. However, this convenience could create risks for the user.

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On Location, Time, and Membership: Studying How Aggregate Location Data Can Harm Users’ Privacy

The increasing availability of location and mobility data enables a number of applications, e.g., enhanced navigation services and parking, context-based recommendations, or waiting time predictions at restaurants, which have great potential to improve the quality of life in modern cities. However, the large-scale collection of location data also raises privacy concerns, as mobility patterns may reveal sensitive attributes about users, e.g., home and work places, lifestyles, or even political or religious inclinations.

Service providers, i.e., companies with access to location data, often use aggregation as a privacy-preserving strategy to release these data to third-parties for various analytics tasks. The idea being that, by grouping together users’ traces, the data no longer contains information to enable inferences about individuals such as the ones mentioned above, while it can be used to obtain useful insights about the crowds. For instance, Waze constructs aggregate traffic models to improve navigation within cities, while Uber provides aggregate data for urban planning purposes. Similarly, CityMapper’s Smart Ride application aims at identifying gaps in transportation networks based on traces and rankings collected by users’ mobile devices, while Telefonica monetizes aggregate location statistics through advertising as part of the Smart Steps project.

That’s great, right? Well, our paper, “Knock Knock, Who’s There? Membership Inference on Aggregate Location Data” and published at NDSS 2018, shows that aggregate location time-series can in fact be used to infer information about individual users. In particular, we demonstrate that aggregate locations are prone to a privacy attack, known as membership inference: a malicious entity aims at identifying whether a specific individual contributed her data to the aggregation. We demonstrate the feasibility of this type of privacy attack on a proof-of-concept setting designed for an academic evaluation, and on a real-world setting where we apply membership inference attacks in the context of the Aircloak challenge, the first bounty program for anonymized data re-identification.

Membership Inference Attacks on Aggregate Location Time-Series

Our NDSS’18 paper studies membership inference attacks on aggregate location time-series indicating the number of people transiting in a certain area at a given time. That is, we show that an adversary with some “prior knowledge” about users’ movements is able to train a machine learning classifier and use it to infer the presence of a specific individual’s data in the aggregates.

We experiment with different types of prior knowledge. On the one hand, we simulate powerful adversaries that know the real locations for a subset of users in a database during the aggregation period (e.g., telco providers which have location information about their clients), while on the other hand, weaker ones which only know past statistics about user groups (i.e., reproducing a setting of continuous data release). Overall, we find that the adversarial prior knowledge influences significantly the effectiveness of the attack.

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Measuring and Modeling the Vivino Wine Social Network

Over the past few years, food and drink have become an essential part of our social media footprints. This shouldn’t come as a surprise – after all, eating and drinking were social activities long before the first #foodporn hashtag on Instagram. In fact, scientific studies have showed that what we gobble up or gulp down is shaped by social and regional influences, and how we tend to mirror habits of people with shared social connections.

Nowadays, we have an unprecedented opportunity to study eating & drinking habits at scale, as people share more and more of that online, both on popular social networks like Instagram, Twitter, and Facebook, but also on “dedicated” apps like Yummly or Untappd.

Along these lines is our recent paper, “Of Wines and Reviews: Measuring and Modeling the Vivino Wine Social Network,” recently presented at the IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining (ASONAM 2018) in Barcelona. The study – co-authored by former UCL undergraduate student Neema Kotonya, Italian wine journalist Paolo De Cristofaro, and UCL faculty Emiliano De Cristofaro –  presented a preliminary study showcasing big-data and social network analysis of how users worldwide consume, rate, and provide reviews of wines. We did so through the lens of Vivino, a popular wine social network. (And, yes, Paolo is Emiliano’s brother! 😊)

What is Vivino?

Vivino.com is an online community for wine enthusiasts, available both as a web and a mobile application. It was founded in 2009 by Heini Zachariassen, with his colleague Theis Sondergaard joining in 2010. In a nutshell, Vivino allows users to review and purchase wines through third-party vendors. The mobile app also provides a “wine scanner” functionality – i.e., users can upload pictures of wine labels and access reviews and details about the wine/winery.

But Vivino is actually a social network, as it allows wine enthusiasts to communicate with and follow each other, as well as share reviews and recommendations. As of September 2018, it had 32 million users, 9.7 million wines covering a multitude of wine styles, grapes, and geographical regions, as well as 103.7 million ratings and almost 35 million reviews.

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Stronger Password, Longer Lifetime: Studying UCL’s password policy

In October 2016, UCL’s Information Services Division (ISD) implemented a new password policy to encourage users to choose stronger passwords. The policy links password lifetime (the time before the password expires) to password strength: The stronger the password, the longer the lifetime.

We (Ingolf Becker, Simon Parkin and M. Angela Sasse) decided to collaborate with the Information Services Division to study the effect of this policy change, and the results were published at USENIX Security this week. We find that users appreciate the choice and respond to the policy by choosing stronger passwords when changing passwords. Even after 16 months the mean password lifetime at UCL continues to increase, yet stronger passwords also lead to more password resets.

The new policy

In the new policy, passwords with Shannon Information Entropy of 50 bits receive a lifetime of 100 days, and passwords with 120 bits receive a lifetime of 350 days:

Password expiry by entropy

Additionally, the new policy penalises the lifetime of passwords containing words from a large dictionary.

Users play the game

We analysed the password lifetime – what we will refer to from here on in as the ‘password strength’ – of all password change and reset events of all pseudonymised users at UCL. The following figure shows the mean password expiration of all users over time, smoothed by 31-day moving averages:

Password expiration over time for all users and new users.

A small drop in password strength was observed between November ’16 and February ’17, as users were moved on to and generally became accustomed to the new system; the kinds of passwords they would have been used to using were at that point not getting them as many days as before (hence the drop). After February ’17, the mean strength increases from 145 days to 170 days in 12 months – an increase of 6.9 bits of entropy. This strongly suggests that users have generally adapted slowly to the new password policy, and eventually make use of the relatively new ability to increase password lifetime by expanding and strengthening their passwords.

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What can infosec learn from strategic theory?

Antonio Roque, of MIT Lincoln Labs, has published some provocative papers to arXiv over the last year. These include one on cybersecurity meta-methodology and one on making predictions in cybersecurity. These papers ask some good questions. The one I want to focus on in this short space is what cybersecurity can learn from Carl von Clausewitz’s treatise On War.

This might seem a bit odd to modern computer scientists, but I think it’s a plausible question. Cybersecurity is about winning conflicts, at least sometimes. And as I and others have written, one of the interesting challenges about generating knowledge with a science of security is the fact we have active adversaries. As Roque tells us, generating knowledge in the face of adversaries is also one of the things On War is about.

One important question for me is whether Clausewitz interestingly presaged our current problems (and has since been overtaken), or if On War makes contributions to thinking about cybersecurity that are new and comparable to those from the fields of economics, mathematics, philosophy of science, etc. After a close reading of these papers, my stance is: I have more questions that need answers.

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An untapped resource to reproduce studies

Science is generally accepted to operate by conducting specially-designed structured observations (such as experiments and case studies) and then interpreting the results to build generalised knowledge (sometimes called theories or models). An important, nay necessary, feature of the social operation of science is transparency in the design, conduct, and interpretation of these structured observations. We’re going to work from the view that security research is science just like any other, though of course as its own discipline it has its own tools, topics, and challenges. This means that studies in security should be replicable, reproducible, or at least able to be corroborated. Spring and Hatleback argue that transparency is just as important for computer science as it is for experimental biology. Rossow et al. also persuasively argue that transparency is a key feature for malware research in particular. But how can we judge whether a paper is transparent enough? The natural answer would seem to be if it is possible to make a replication attempt from the materials and information in the paper. Forget how often the replications succeed for now, although we know that there are publication biases and other factors that mess with that.

So how many security papers published in major conferences contain enough information to attempt a reproduction? In short, we don’t know. From anecdotal evidence, Jono and a couple students looked through the IEEE S&P 2012 proceedings in 2013, and the results were pretty grim. But heroic effort from a few interested parties is not a sustainable answer to this question. We’re here to propose a slightly more robust solution. Master’s students in security should attempt to reproduce published papers as their capstone thesis work. This has several benefits, and several challenges. In the following we hope to convince you that the challenges can be mitigated and the benefits are worth it.

This should be a choice, but one that master’s students should want to make. If anyone has a great new idea to pursue, they should be encouraged to do so. However, here in the UK, the dissertation process is compressed into the summer and there’s not always time to prototype and pilot study designs. Selecting a paper to reproduce, with a documented methodology in place, lets the student get to work faster. There is still a start-up cost; students will likely have to read several abstracts to shortlist a few workable papers, and then read these few papers in detail to select a good candidate. But learning to read, shortlist, and study academic papers is an important skill that all master’s students should be attempting to, well, master. This style of project would provide them with an opportunity to practice these skills.

Briefly, let’s be clear what we mean by reproduction of published work.
Reproduction isn’t just one thing. There’s reproduce and replicate and corroborate and controlled variation (see Feitelson for details). Not everything is amenable to reproduction. For example, case studies (such as attack papers) or natural experiments are often interesting because they are unique. Corroborating some aspect of the case may be possible with a new study, and such study is also valuable. But this not the sort of reproduction we have in mind to advocate here.

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