When you are a medical doctor, friends and family invariably ask you about their aches and pains. When you are a computer specialist, they ask you to fix their computer. About ten years ago, most of the questions I was getting from friends and family as a security techie had to do with frustration over passwords. I observed that what techies had done to the rest of humanity was not just wrong but fundamentally unethical: asking people to do something impossible and then, if they got hacked, blaming them for not doing it.
So in 2011, years before the Fido Alliance was formed (2013) and Apple announced its smartwatch (2014), I published my detailed design for a clean-slate password replacement I calledPico, an alternative system intended to be easier to use and more secure than passwords. The European Research Council was generous enough to fund my vision with a grant that allowed me to recruit and lead a team of brilliant researchers over a period of five years. We built a number of prototypes, wrote a bunch of papers, offered projects to a number of students and even launched a start-up and thereby learnt a few first-hand lessons about business, venture capital, markets, sales and the difficult process of transitioning from academic research to a profitable commercial product. During all those years we changed our minds a few times about what ought to be done and we came to understand a lot better both the problem space and the mindset of the users.
When you visit a website, your web browser provides a range of information to the website, including the name and version of your browser, screen size, fonts installed, and so on. Website authors can use this information to provide an improved user experience. Unfortunately this same information can also be used to track you. In particular, this information can be used to generate a distinctive signature, or device fingerprint, to identify you.
We have developed a new type of fingerprinting attack, the calibration fingerprinting attack. Our attack uses data gathered from the accelerometer, gyroscope and magnetometer sensors found in smartphones to construct a globally unique fingerprint. Our attack can be launched by any website you visit or any app you use on a vulnerable device without requiring any explicit confirmation or consent from you. The attack takes less than one second to generate a fingerprint which never changes, even after a factory reset. This attack therefore provides an effective means to track you as you browse across the web and move between apps on your phone.
Our approach works by carefully analysing the data from sensors which are accessible without any special permissions on both websites and apps. Our analysis infers the per-device factory calibration data which manufacturers embed into the firmware of the smartphone to compensate for systematic manufacturing errors. This calibration data can then be used as the fingerprint.
In general, it is difficult to create a unique fingerprint on iOS devices due to strict sandboxing and device homogeneity. However, we demonstrated that our approach can produce globally unique fingerprints for iOS devices from an installed app: around 67 bits of entropy for the iPhone 6S. Calibration fingerprints generated by a website are less unique (around 42 bits of entropy for the iPhone 6S), but they are orthogonal to existing fingerprinting techniques and together they are likely to form a globally unique fingerprint for iOS devices. Apple adopted our proposed mitigations in iOS 12.2 for apps (CVE-2019-8541). Apple recently removed all access to motion sensors from Mobile Safari by default.
We presented this work on 21st May at IEEE Symposium on Security and Privacy 2019. For more details, please visit the SensorID website and read our paper:
We’re looking for a Chief Information Security Officer. This isn’t a research post here at the lab, but across the yard in University Information Services, where they manage our networks and our administrative systems. There will be opportunities to work with security researchers like us, but the main task is protecting Cambridge from all sorts of online bad actors. If you would like to be in the thick of it, and you know what you’re doing, here’s how you can apply.
I really like the simplicity of the original assumption. The starting point of the research was that different crypto/RSA libraries use slightly different elimination methods and “cut-off” thresholds to find suitable prime numbers. They thought these differences should be sufficient to detect a particular cryptographic implementation and all that was needed were public keys. Petr et al confirmed this assumption. The best paper award is a well-deserved recognition as I’ve worked with and followed Petr’s activities closely.
The authors created a method for efficient identification of the source (software library or hardware device) of RSA public keys. It resulted in a classification of keys into more than dozen categories. This classification can be used as a fingerprint that decreases the anonymity of users of Tor and other privacy enhancing mailers or operators.
All that is a result of an analysis of over 60 million freshly generated keys from 22 open- and closed-source libraries and from 16 different smart-cards. While the findings are fairly theoretical, they are demonstrated with a series of easy to understand graphs (see above).
I can’t see an easy way to exploit the results for immediate cyber attacks. However, we started looking into practical applications. There are interesting opportunities for enterprise compliance audits, as the classification only requires access to datasets of public keys – often created as a by-product of internal network vulnerability scanning.
I am at the Privacy Enhancing Technologies Symposium (PETS 2016) in Darmstadt until Friday, and will try to liveblog some of the sessions in followups to this post. (I can’t do them all as there are some parallel sessions.)
A lot of people are starting to ask about the security and privacy implications of the “Internet of Things”. Once there’s software in everything, what will go wrong? We’ve seen a botnet recruiting CCTV cameras, and a former Director of GCHQ recently told a parliamentary committee that it might be convenient if a suspect’s car could be infected with malware that would cause it to continually report its GPS position. (The new InvestigatoryPowersBill will give the police and the spooks the power to hack any device they want.)
So here is the video of a talk I gave on The Internet of Bad Things to the Virus Bulletin conference. As the devices around us become smarter they will become less loyal, and it’s not just about malware (whether written by cops or by crooks). We can expect all sorts of novel business models, many of them exploitative, as well as some downright dishonesty: the recent Volkswagen scandal won’t be the last.
But dealing with pervasive malware in everything will demand new approaches. Our approach to the Internet of Bad Things includes our new Cambridge Cybercrime Centre, which will let us monitor bad things online at the kind of scale that will be required.
First, the Password Hashing Competition “have selected Argon2 as a basis for the final PHC winner”, which will be “finalized by end of Q3 2015”. This is about selecting a new password hashing scheme to improve on the state of the art and make brute force password cracking harder. Hopefully we’ll have some good presentations about this topic at the conference.
Second, and unrelated: Per Thorsheim and Paul Moore have launched a privacy-protecting Chrome plugin called Keyboard Privacy to guard your anonymity against websites that look at keystroke dynamics to identify users. So, you might go through Tor, but the site recognizes you by your typing pattern and builds a typing profile that “can be used to identify you at other sites you’re using, were identifiable information is available about you”. Their plugin intercepts your keystrokes, batches them up and delivers them to the website at a constant pace, interfering with the site’s ability to build a profile that identifies you.
Today we unveil a major report on whether law enforcement and intelligence agencies should have exceptional access to cryptographic keys and to our computer and communications data generally. David Cameron has called for this, as have US law enforcement leaders such as FBI Director James Comey.
This policy repeats a mistake of the 1990s. The Clinton administration tried for years to seize control of civilian cryptography, first with the Clipper Chip, and then with various proposals for ‘key escrow’ or ‘trusted third party encryption’. Back then, a group of experts on cryptography and computer security got together to explain why this was a bad idea. We have now reconvened in response to the attempt by Cameron and Comey to resuscitate the old dead horse of the 1990s.
Our report is also highly relevant to the new ‘Snoopers’ Charter’ that Home Secretary Teresa May has promised to put before parliament this fall. Mrs May has made clear she wantsaccess to everything.
However this is both wrong in principle, and unworkable in practice. Building back doors into all computer and communication systems is against most of the principles of security engineering, and it also against the principles of human rights. Our right to privacy, set out in section 8 of the European Convention on Human Rights, can only be overridden by mechanisms that meet three tests. First, they must be set out in law, with sufficient clarity for their effects to be foreseeable; second, they must be proportionate; third, they must be necessary in a democratic society. As our report makes clear, universal exceptional access will fail all these tests by a mile.