This week, my contribution to our three-paper Thursday research reading list series is on capability systems. Capabilities are unforgeable tokens of authority — capability systems are hardware, operating, or programming systems in which access to resources can occur only using capabilities. Capability system research in the 1970s motivated many fundamental insights into practical articulations of the principle of least privilege, separation of mechanism and policy, and the interactions between program representation and security. They also formed the intellectual foundation for a recent renaissance in capability-oriented microkernels (L4, sel4) and programming languages (Joe-E, Caja, ECMAScript 5). Capability systems have a long history at Cambridge, including the CAP Computer, and more recently, our work on Capsicum: practical capabilities for UNIX. I’ve selected three “must read” papers, but there are plenty of other influential pieces that, unfortunately, space doesn’t allow for!
Continue reading Three-paper Thursday: capability systems
Monthly Archives: February 2012
Social authentication – harder than it looks!
This is the title of a paper we’ll be presenting next week at the Financial Crypto conference (slides). There is also coverage in the New Scientist.
Facebook has a social authentication mechanism where you may be asked to recognise some of your friends from photos as part of the login process. We analysed this and found it to be vulnerable to guessing by your friends, and also to modern face-recognition systems. Most people want privacy only from those close to them; if you’re having an affair then you want your partner to not find out but you don’t care if someone in Mongolia learns about it. And if your partner finds out and becomes your ex, then you don’t want them to be able to cause havoc on your account. Celebrities are similar, except that everyone is their friend (and potentially their enemy).
Second, if someone outside your circle of friends is doing a targeted attack on you, then by friending your friends they can get some access to your social circle to collect photos, which they might use in image-recognition software or even manually to pass the test.
Continue reading Social authentication – harder than it looks!
How hard are PINs to guess?
Note: this research was also blogged today at the NY Times’ Bits technology blog.
I’ve personally been researching password statistics for a few years now (as well as personal knowledge questions) and our research group has a long history of research on banking security. In an upcoming paper at next weel’s Financial Cryptography conference written with Sören Preibusch and Ross Anderson, we’ve brought the two research threads together with the first-ever quantitative analysis of the difficulty of guessing 4-digit banking PINs. Somewhat amazingly given the importance of PINs and their entrenchment in infrastructure around the world, there’s never been an academic study of how people actually choose them. After modeling banking PIN selection using a combination of leaked data from non-banking sources and a massive online survey, we found that people are significantly more careful choosing PINs then online passwords, with a majority using an effectively random sequence of digits. Still, the persistence of a few weak choices and birthdates in particular suggests that guessing attacks may be worthwhile for an opportunistic thief. Continue reading How hard are PINs to guess?
Cloudy with a Chance of Privacy
Three Paper Thursday is an experimental new feature in which we highlight research that group members find interesting.
When new technologies become popular, we privacy people are sometimes miffed that nobody asked for our opinions during the design phase. Sometimes this leads us to make sweeping generalisations such as “only use the Cloud for things you don’t care about protecting” or “Facebook is only for people who don’t care about privacy.” We have long accused others of assuming that the real world is incompatible with privacy, but are we guilty of assuming the converse?
On this Three Paper Thursday, I’d like to highlight three short papers that challenge these zero-sum assumptions. Each is eight pages long and none requires a degree in mathematics to understand; I hope you enjoy them.