Category Archives: Academic papers

Why bouncing droplets are a pretty good model of quantum mechanics

Academic papers, Cryptology

Today Robert Brady and I publish a paper that solves an outstanding problem in physics. We explain the beautiful bouncing droplet experiments of Yves Couder, Emmanuel Fort and their colleagues.

For years now, people interested in the foundations of physics have been intrigued by the fact that droplets bouncing on a vibrating tray of fluid can behave in many ways like quantum mechanical particles, with single-slit and double-slit diffraction, tunneling, Anderson localisation and quantised orbits.

In our new paper, Robert Brady and I explain why. The wave field surrounding the droplet is, to a good approximation, Lorentz covariant with the constant c being the speed of surface waves. This plus the inverse square force between bouncing droplets (which acts like the Coulomb force) gives rise to an analogue of the magnetic force, which can be observed clearly in the droplet data. There is also an analogue of the Schrödinger equation, and even of the Pauli exclusion principle.

These results not only solve a fascinating puzzle, but might perhaps nudge more people to think about novel models of quantum foundations, about which we’ve written three previous papers.

Reading this may harm your computer

Academic papers, Legal issues, Security economics, Security psychology

David Modic and I have just published a paper on The psychology of malware warnings. We’re constantly bombarded with warnings designed to cover someone else’s back, but what sort of text should we put in a warning if we actually want the user to pay attention to it?

To our surprise, social cues didn’t seem to work. What works best is to make the warning concrete; people ignore general warnings such as that a web page “might harm your computer” but do pay attention to a specific one such as that the page would “try to infect your computer with malware designed to steal your bank account and credit card details in order to defraud you”. There is also some effect from appeals to authority: people who trust their browser vendor will avoid a page “reported and confirmed by our security team to contain malware”.

We also analysed who turned off browser warnings, or would have if they’d known how: they were people who ignored warnings anyway, typically men who distrusted authority and either couldn’t understand the warnings or were IT experts.

2013 Capsicum year in review

Academic papers, Open-source security, Operating systems, Security engineering

It’s been a busy year for Capsicum, practical capabilities for UNIX, so a year-end update seemed in order:

The FreeBSD Foundation and Google jointly funded a Capsicum Integration Project that took place throughout 2013 — described by Foundation project technical director Ed Maste in a recent blog article. Pawel Jakub Dawidek refined several Capsicum APIs, improving support for ioctls and increasing the number of supported capability rights for FreeBSD 10. He also developed Casper, a helper daemon that provides services (such as DNS, access to random numbers) to sandboxes — and can, itself, sandbox services. Casper is now in the FreeBSD 11.x development branch, enabled by default, and should appear in FreeBSD 10.1. The Google Open Source Program Office (OSPO) blog also carried a September 2013 article on their support for open-source security, featuring Capsicum.

Capsicum is enabled by default in the forthcoming FreeBSD 10.0 release — capability mode, capabilities, and process descriptors are available in the out-of-the-box GENERIC kernel. A number of system services use Capsicum to sandbox themselves — such as the DHCP client, high-availability storage daemon, audit log distribution daemon, but also command-line tools like kdump and tcpdump that handle risky data. Even more will appear in FreeBSD 10.1 next year, now that Casper is available.

David Drysdale at Google announced Capsicum for Linux, an adaptation of Linux to provide Capsicum’s capability mode and capabilities, in November 2013. David and Ben Laurie visited us in Cambridge multiple times this year to discuss the design and implementation, review newer Capsicum APIs, and talk about future directions. They hope to upstream this work to the Linux community. Joris Giovannangeli also announced an adaptation of Capsicum to DragonFlyBSD in October 2013.

Over the summer, Mariusz Zaborski and Daniel Peryolon were funded by Google Summer of Code to work on a variety of new Capsicum features and services, adapting core UNIX components and third-party applications to support sandboxing. For example, Mariusz looked at sandboxing BSD grep: if a vulnerability arises in grep’s regular-expression matching, why should processing a file of malicious origin yield full rights to your UNIX account?

In May 2013, our colleagues at the University of Wisconsin, Madison, led by Bill Harris, published a paper at the IEEE Symposium on Security and Privacy (“Oakland”) on “Declarative, Temporal, and Practical Programming with Capabilities” — how to model program behaviour, and automatically transform some classes of applications to use Capsicum sandboxing. We were very pleased to lend a hand with this work, and feel the art of programming for compartmentalisation is a key research challenge. We also collaborated with folk at SRI and Google on a a workshop paper developing our ideas about application compartmentalisation, which appeared at the Security Protocols Workshop here in Cambridge in March 2013.

Google and the FreeBSD Foundation are committed to further work on Capsicum and its integration with applications, and research continues on how to apply Capsicum at several institutions including here at Cambridge. We hope to kick off a new batch of application adaptation in coming months — as well as integration with features such as DNSSEC. However, we also need your help in adapting applications to use Capsicum on systems that support it!

WEIS 2014 call for papers

Academic papers, Call for papers, Security economics

Next year’s Workshop on the Economics of Information Security (WEIS 2014) will be at Penn State on June 23–24. The call for papers is now out; papers are due by the end of February.

It will be fascinating to see what effects the Snowden revelations will have on the community’s thinking about security standards and regulation, the incentives for information sharing and cooperation, and the economics of privacy, to mention only three of the workshop’s usual topics. Now that we’ve had six months to think things through, how do you think the security game has changed, and why? Do we need minor changes to our models, or major ones? Are we in the same policy world, or a quite different one? WEIS could be particularly interesting next year. Get writing!

A new side channel attack

Academic papers, Banking security, Hardware & signals, Operating systems, Privacy technology, Security engineering, Usability

Today we’re presenting a new side-channel attack in PIN Skimmer: Inferring PINs Through The Camera and Microphone at SPSM 2013. We found that software on your smartphone can work out what PIN you’re entering by watching your face through the camera and listening for the clicks as you type. Previous researchers had shown how to work out PINs using the gyro and accelerometer; we found that the camera works about as well. We watch how your face appears to move as you jiggle your phone by typing.

There are implications for the design of electronic wallets using mechanisms such as Trustzone which enable some apps to run in a more secure sandbox. Such systems try to prevent sensitive data such as bank credentials being stolen by malware. Our work shows it’s not enough for your electronic wallet software to grab hold of the screen, the accelerometers and the gyro; you’d better lock down the video camera, and the still camera too while you’re at it. (Our attack can use the still camera in burst mode.)

We suggest ways in which mobile phone operating systems might mitigate the risks. Meanwhile, if you’re developing payment apps, you’d better be aware that these risks exist.

Offender tagging 2.0

Academic papers, Legal issues, News coverage, Security engineering

Three of our clients have been acquitted of tampering with curfew tags after the Ministry of Justice and G4S were unwilling to have an independent forensic team examine their evidence. This brings to five the number of tag-tampering prosecutions that have been withdrawn or collapsed when the defence says “Right, prove it then.” I reported the first case here.

The three latest matters were high-profile terrorism cases, involving three of the nine men tagged under the new Terrorism Prevention and Investigation Measure (TPIM) – a kind of national-security ASBO handed out by MI5, and which had already been criticised by David Anderson QC, the government’s independent reviewer of terrorism legislation, for low standards of proof. Unlike a normal ASBO which a court gives “on the balance of probabilities”, you can get a TPIM if the Home Secretary declares she has a “reasonable suspicion”.

The Ministry of Justice should perhaps, when they let the tagging contracts, have read our 1994 paper on the John Munden case, or the post here about the similar case of Jane Badger. If you’re designing a system one of whose functions is to provide evidence, you’d better design it to withstand hostile review. “Trust us” doesn’t cut it in criminal trials, and neither does “I’m afraid that’s commercially confidential.”

How to deal with emergencies better

Academic papers, Legal issues, News coverage, Politics, Security psychology

Britain has just been hit by a storm; two people have been killed by falling trees, and one swept out to sea. The rail network is in chaos and over 100,000 homes lost electric power. What can security engineering teach about such events?

Risk communication could be very much better. The storm had been forecast for several days but the instructions and advice from authority have almost all been framed in vague and general terms. Our research on browser warnings shows that people mostly ignore vague warnings (“Warning – visiting this web site may harm your computer!”) but pay much more attention to concrete ones (such as “The site you are about to visit has been confirmed to contain software that poses a significant risk to you, with no tangible benefit. It would try to infect your computer with malware designed to steal your bank account and credit card details in order to defraud you”). In fact, making warnings more concrete is the only thing that works here – nudge favourites such as appealing to social norms, or authority, or even putting a cartoon face on the page to activate social cognition, don’t seem to have a significant effect in this context.

So how should the Met Office and the emergency services deal with the next storm?

Continue reading How to deal with emergencies better →

A Study of Whois Privacy and Proxy Service Abuse

Academic papers, Security economics, Web security

ICANN have now published a draft for public comment of “A Study of Whois Privacy and Proxy Service Abuse“. I am the primary author of this report — the work being done whilst I was collaborating with the National Physical Laboratory (NPL) under EPSRC Grant EP/H018298/1.

This particular study was originally proposed by ICANN in 2010, one of several that were to examine the impact of domain registrants using privacy services (where the name of a domain registrant is published, but contact details are kept private) and proxy services (where even the domain licensee’s name is not made available on the public database).

ICANN wanted to know if a significant percentage of the domain names used to conduct illegal or harmful Internet activities are registered via privacy or proxy services to obscure the perpetrator’s identity? No surprises in our results: they are!

However, it’s more interesting to ask whether this percentage is somewhat higher than the usage of privacy or proxy services for entirely lawful and harmless Internet activities? This turned out NOT to be the case — for example banks use privacy and proxy services almost as often as the registrants of domains used in the hosting of child sexual abuse images; and the registrants of domains used to host (legal) adult pornography use privacy and proxy services more often than most (but not all) of the different types of malicious activity that we studied.

It’s also relevant to consider what other methods might be chosen by those involved in criminal activity to obscure their identities, because in the event of changes to privacy and proxy services, it is likely that they will turn to these alternatives.

Accordingly, we determined experimentally whether a significant percentage of the domain names we examined have been registered with incorrect Whois contact information – and specifically whether or not we could reach the domain registrant using a phone number from the Whois information. We asked them a single question in their native language “did you register this domain”?

We got somewhat variable results from our phone survey — but the pattern becomes clear if we consider whether there is any a priori hope at all of ringing up the domain registrant?

If we sum up the likelihoods:

  • uses privacy or proxy service
  • no (apparently valid) phone number in whois
  • number is apparently valid, but fails to connect
  • number reaches someone other than the registrant

then we find that for legal and harmless activities the probability of a phone call not being possible ranges between 24% (legal pharmacies on the Legitscript list) and 62% (owners of lawful websites that someone has broken into and installed phishing pages). For malicious activities the probability of failure is 88% or more, with typosquatting (which is a civil matter, rather than a criminal one) sitting at 68% (some of the typosquatters want to hide, some do not).

There’s lots of detail and supporting statistics in the report… and an executive summary for the time-challenged. It will provide real data, rather than just speculative anecdotes, to inform the debate around reforming Whois — and the difficulties of doing so.

NSA Award for Best Scientific Cybersecurity Paper

Academic papers, Authentication, Awards

Yesterday I received the NSA award for the Best Scientific Cybersecurity Paper of 2012 for my IEEE Oakland paper “The science of guessing.” I’m honored to have been recognised by the distinguished academic panel assembled by the NSA. I’d like to again thank Henry Watts, Elizabeth Zwicky, and everybody else at Yahoo! who helped me with this research while I interned there, as well as Richard Clayton and Ross Anderson for their support and supervision throughout.

On a personal note, I’d be remiss not to mention my conflicted feelings about winning the award given what we know about the NSA’s widespread collection of private communications and what remains unknown about oversight over the agency’s operations. Like many in the community of cryptographers and security engineers, I’m sad that we haven’t better informed the public about the inherent dangers and questionable utility of mass surveillance. And like many American citizens I’m ashamed we’ve let our politicians sneak the country down this path.

In accepting the award I don’t condone the NSA’s surveillance. Simply put, I don’t think a free society is compatible with an organisation like the NSA in its current form. Yet I’m glad I got the rare opportunity to visit with the NSA and I’m grateful for my hosts’ genuine hospitality. A large group of engineers turned up to hear my presentation, asked sharp questions, understood and cared about the privacy implications of studying password data. It affirmed my feeling that America’s core problems are in Washington and not in Fort Meade. Our focus must remain on winning the public debate around surveillance and developing privacy-enhancing technology. But I hope that this award program, established to increase engagement with academic researchers, can be a small but positive step.