Light Blue Touchpaper

I am one of 38 researchers and academics (almost all of whom are far more important and famous than I will ever be!), who has signed an Open Letter to Google’s CEO, Eric Schmidt.

The letter, whose text is released today, calls upon Google to honour the important privacy promises it has made to its customers and protect users’ communications from theft and snooping by enabling industry standard transport encryption technology (HTTPS) for Google Mail, Docs, and Calendar.

Google already uses HTTPS for sign-in, but the options to make the whole of the session secure are hidden away where few people will ever find them.

Hence, at the moment pretty much everyone who uses a public WiFi connection to read their Gmail or edit a shared doc has no protection at all if any passing stranger decides to peek and see what they’re doing.

However, getting everyone to change their behaviour will take lots of explaining. Much simpler to have Google edit a couple of configuration files and flip a default the other way.

The letter goes into the issues in considerable detail (it’s eleven pages long with all the footnotes)… Eric Schmidt can hardly complain that we’ve failed to explain the issues to him !

I’m at SHB 2009, which brings security engineers together with psychologists, behavioral economists and others interested in deception, fraud, fearmongering, risk perception and how we make security systems more usable. Here is the agenda.

This workshop was first held last year, and most of us who attended reckoned it was the most exciting event we’d been to in some while. (I blogged SHB 2008 here.) In followups that will appear as comments to this post, I’ll be liveblogging SHB 2009.

One of the defining features of Web 2.0 is user-uploaded content, specifically photos. I believe that photo-sharing has quietly been the killer application which has driven the mass adoption of social networks. Facebook alone hosts over 40 billion photos, over 200 per user, and receives over 25 million new photos each day. Hosting such a huge number of photos is an interesting engineering challenge. The dominant paradigm which has emerged is to host the main website from one server which handles user log-in and navigation, and host the images on separate special-purpose photo servers, usually on an external content-delivery network. The advantage is that the photo server is freed from maintaining any state. It simply serves its photos to any requester who knows the photo’s URL.

This setup combines the two classic forms of enforcing file permissions, access control lists and capabilities. The main website checks each request for a photo against an ACL, it then grants a capability to view a photo in the form of an obfuscated URL which can be sent to the photo-server. We wrote earlier about how it was possible to forge Facebook’s capability-URLs and gain unauthorised access to photos. Fortunately, this has been fixed and it appears that most sites use capability-URLs with enough randomness to be unforgeable. There’s another traditional problem with capability systems though: revocation. My colleagues Jonathan Anderson, Andrew Lewis, Frank Stajano and I ran a small experiment on 16 social-networking, blogging, and photo-sharing web sites and found that most failed to remove image files from their photo servers after they were deleted from the main web site. It’s often feared that once data is uploaded into “the cloud,” it’s impossible to tell how many backup copies may exist and where, and this provides clear proof that content delivery networks are a major problem for data remanence. (more…)

I was recently asked for a brief (4-page) invited paper for a forthcoming special issue of the ACM SIGSPATIAL on privacy and security of location-based systems, so I wrote Foot-driven computing: our first glimpse of location privacy issues.

In 1989 at ORL we developed the Active Badge, the first indoor location system: an infrared transmitter worn by personnel that allowed you to tell which room the wearer was in. Every press and TV reporter who visited our lab worried about the intrusiveness of this technology; yet, today, all those people happily carry mobile phones through which they can be tracked anywhere they go. The significance of the Active Badge project was to give us a head start of a few years during which to think about location privacy before it affected hundreds of millions of people. (There is more on our early ubiquitous computing work at ORL in this free excerpt from my book.)

Location privacy is a hard problem to solve, first because ordinary people don’t seem to actually care, and second because there is a misalignment of incentives: those who could do the most to address the problem are the least affected and the least concerned about it. But we have a responsibility to address it, in the same way that designers of new vehicles have a responsibility to address the pollution and energy consumption issue.

Facebook has been serving up public listings for over a year now. Unlike most of the site, anybody can view public listings, even non-members. They offer a window into the Facebook world for those who haven’t joined yet, since Facebook doesn’t allow full profiles to be publicly viewable by non-members (unlike MySpace and others). Of course, this window into Facebook comes with a prominent “Sign Up” button, growth still being the main mark of success in the social networking world. The goal is for non-members to stumble across a public listing, see how many friends are already using Facebook, and then join. Economists call this a network effect, and Facebook is shrewdly harnessing it.

Of course, to do this, Facebook is making public every user’s name, photo, and 8 friendship links. Affiliations with organizations, causes, or products are also listed, I just don’t have any on my profile (though my sister does). This is quite a bit of information given away by a feature many active Facebook user are unaware of. Indeed, it’s more information than the Facebook’s own privacy policy indicates is given away. When the feature was launched in 2007, every over-18 user was automatically opted-in, as have been new users since then. You can opt out, but few people do-out of more than 500 friends of mine, only 3 had taken the time to opt out. It doesn’t help that most users are unaware of the feature, since registered users don’t encounter it.

Making matters worse, public listings aren’t protected from crawling. In fact they are designed to be indexed by search engines. In our own experiments, we were able to download over 250,000 public listings per day using a desktop PC and a fairly crude Python script. For a serious data aggregator getting every user’s listing is no sweat. So what can one do with 200 million public listings?

I explored this question along with Jonathan Anderson, Frank Stajano, and Ross Anderson in a new paper which we presented today at the ACM Social Network Systems Workshop in Nuremberg. Facebook’s public listings give us a random sample of the social graph, leading to some interesting exercises in graph theory. As we describe in the paper, it turns out that this sampled graph allows us to approximate many properties of the complete network surprisingly well: degree and centrality of nodes, small dominating sets, short paths, and community structure. These are all things marketers and sociologists alike would love to know for the complete Facebook graph.

This result leads to two interesting conclusions. First, protecting a social graph is hard. Consistent with previous results, we found that giving away a seemingly small amount can allow much information to be inferred. It’s also been shown that anonymising a social graph is almost impossible.

Second, Facebook is developing a track record of releasing features and then being surprised by the privacy implications, from Beacon to NewsFeed and now Public Search. Analogous to security-critical software, where new code is extensively tested and evaluated before being deployed, social networks should have a formal privacy review of all new features before they are rolled out (as, indeed, should other web services which collect personal information).  Features like public search listings shouldn’t make it off the drawing board.

The EFF and the Tor Project have been accepted into Google Summer of Code. This programme offers students a stipend for contributing to open source software over a 3 month period. Google Summer of Code has been running since 2005 and the Tor project has been a participant since 2007.

We are looking for talented and motivated students to work on a number of projects to improve Tor, and related applications. Students are also welcome to come up with their own ideas. Applications must be submitted by 3 April 2009. For further information, and details on how to apply, see the Tor blog.

HotPETs – the 2nd Hot Topics in Privacy Enhancing Technologies (co-located with PETS) will be held in Seattle, 5–7 August 2009.

HotPETs is the forum for new ideas on privacy, anonymity, censorship resistance, and related topics. Work-in-progress is welcomed, and the format of the workshop will be to encourage feedback and discussion. Submissions are especially encouraged on the human side of privacy: what do people believe about privacy? How does privacy work in existing institutions?

Papers (up to 15 pages) are due by 8 May 2009. Further information can be found in the call for papers.

I recently presented a paper on Forensic genomics: kin privacy, driftnets and other open questions (co-authored with Lucia Bianchi, Pietro Liò and Douwe Korff) at WPES 2008, the Workshop for Privacy in the Electronic Society of ACM CCS, the ACM Computer and Communication Security conference. Pietro and I also gave a related talk here at the Computer Laboratory in Cambridge.

While genetics is concerned with the observation of specific sections of DNA, genomics is about studying the entire genome of an organism, something that has only become practically possible in recent years. In forensic genetics, which is the technology behind the large national DNA databases being built in several countries including notably UK and USA (Wallace’s outstanding article lucidly exposes many significant issues), investigators compare scene-of-crime samples with database samples by checking if they match, but only on a very small number of specific locations in the genome (e.g. 13 locations according to the CODIS rules). In our paper we explore what might change when forensic analysis moves from genetics to genomics over the next few decades. This is a problem that can only be meaningfully approached from a multi-disciplinary viewpoint and indeed our combined backgrounds cover computer security, bioinformatics and law.

(Image from Wikimedia commons, in turn from NIST.)

Sequencing the first human genome (2003) cost 2.7 billion dollars and took 13 years. The US’s National Human Genome Research Institute has offered over 20 M$ worth of grants towards the goal of driving the cost of whole-genome sequencing down to a thousand dollars. This will enable personalized genomic medicine (e.g. predicting genetic risk of contracting specific diseases) but will also open up a number of ethical and privacy-related problems. Eugenetic abortions, genomic pre-screening as precondition for healthcare (or even just dating…), (mis)use of genomic data for purposes other than that for which it was collected and so forth. In various jurisdictions there exists legislation (such as the recent GINA in the US) that attempts to protect citizens from some of the possible abuses; but how strongly is it enforced? And is it enough? In the forensic context, is the DNA analysis procedure as infallible as we are led to believe? There are many subtleties associated with the interpretation of statistical results; when even professional statisticians disagree, how are the poor jurors expected to reach a fair verdict? Another subtle issue is kin privacy: if the scene-of-crime sample, compared with everyone in the database, partially matches Alice, this may be used as a hint to investigate all her relatives, who aren’t even in the database; indeed, some 1980s murders were recently solved in this way. “This raises compelling policy questions about the balance between collective security and individual privacy” [Bieber, Brenner, Lazer, 2006]. Should a democracy allow such a “driftnet” approach of suspecting and investigating all the innocents in order to catch the guilty?

This is a paper of questions rather than one of solutions. We believe an informed public debate is needed before the expected transition from genetics to genomics takes place. We want to stimulate discussion and therefore we invite you to read the paper, make up your mind and support what you believe are the right answers.

This week, Nick Clegg, leader of the UK Liberal Democrat Party, and David Howarth, MP for Cambridgeshire, visited our hardware security lab for a demonstration of Chip & PIN fraud techniques.

They used this visit to announce their new party policy on protections against identity fraud. At present, credit rating companies are exempt from aspects of the Data Protection Act and can forward personal information about an individual’s financial history to companies without the subject’s consent. Clegg proposes to give individuals the rights to “freeze” their credit records, making it more difficult for fraudsters to impersonate others.

See also the Cambridge Evening News article and video interview.

I am on the program committee for the 9th Privacy Enhancing Technologies Symposium (PETS 2009), to be held in Seattle, WA, USA, 5–7 August 2009. PETS is the leading venue for research on privacy and anonymity, offering an enjoyable environment and stimulating discussion. If you are working in this field, I can strongly recommend submitting a paper.

This year, we are particularly looking for submissions from topics other than anonymous communications, so if work from your field may be applied, or is otherwise related, to the topic of privacy, I’d encourage you to consider PETS as a potential venue.

The submission deadline for the main session is 2 March 2009. As with last year, we will also have a “HotPETS” event, for new and exciting work in the field which is still in a formative state. Submissions for HotPETS should be received by 8 May 2009.

Further information can be found in the call for papers.