InfoSec group

Nicolas Courtois – Algebraic cryptanalysis is not the best way to break something, but sometimes it is the only option

Nicolas Courtois, a mathematician and senior lecturer in computer science at UCL, working with Daniel Hulme and Theodosis Mourouzis, has won the 2012 best paper award from the International Academy, Research, and Industry Association for their work on using SAT solvers to study various problems in algebra and circuit optimization. The research was funded by the European Commission under the FP7 project number 242497, “Resilient Infrastructure and Building Security (RIBS)” and by the UK Technology Strategy Board under project 9626-58525. The paper, Multiplicative Complexity and Solving Generalized Brent Equations with SAT Solvers, was presented at Computation Tools 2012, the third International Conference on Computational Logics, Algebras, Programming, Tools, and Benchmarking, held in Nice, France in July.

https://www.youtube.com/watch?v=Lfen7ZOIkYw

SAT (short for “satisfiability”) solvers are algorithms used to analyse logical problems composed of multiple statements such as “A is true OR not-B is true or C is true” for the purpose of determining whether the whole system can be true – that is, whether all the statements it’s composed of can be satisfied. SAT solvers also are used to determine how to assign the variables to make the set of statements true. In 2007, Bard and Courtois realised they could be used to test the security of cryptographic functions and measure their complexity, and today they are important tools in cryptanalysis; they have already been used for a long time in other applications such as verifying hardware and software. In this particular paper, Courtois, Hulme, and Mourouzis focused on optimising S-boxes for industrial block ciphers; the paper reports the results of applying their methodology to the PRESENT and GOST block ciphers. Reducing the complexity and hardware cost of these ciphers is particularly important to build so-called secure implementations of cryptography. These are particularly costly because they need to protect against additional threats such as side-channel attacks, in which the attacker exploits additional information leaked from the physical system – for example, by using an oscilloscope to observe a smart card’s behaviour.

“It’s more a discovery than an invention,” says Courtois. “One of the amazing things SAT solvers can do is give you proof that something is not true.” The semiconductor industry provides one application of the work in this paper: these techniques promise to provide a way to test whether a circuit has been built with the greatest possible efficiency by proving that the chip design uses the smallest possible number of logic gates.

“You’ll get optimal designs and be able to prove they cannot be done better,” he says.

Classical cryptanalysis proceeds by finding approximations to the way a cipher works. Many successful academic attacks have been mounted using such techniques, but they rely on having a relatively large amount of data available for study. That works for large archives of stored data – such as, for example, the communications stored and kept by the Allies after World War II for later cryptanalysis. But in many real-world applications, it is more common to have only very small amounts of data.

“The more realistic scenario is that you’ll just have one or a few messages,” says Courtois. Bluetooth, for example, encrypts only 1,500 bits with a single key. “Most attacks are useless because they won’t work with this quantity of data.” Algebraic cryptanalysis, which he explained in New Frontier in Symmetric Cryptanalysis, an invited talk at Indocrypt 2008, by contrast, is one of the few techniques that can be hoped to work in such difficult situations.

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Sarah Meiklejohn – Security and Cryptography

As a child, Sarah Meiklejohn thought she might become a linguist, largely because she was so strongly interested in the work being done to decode the ancient Greek writing systems Linear A and Linear B.

“I loved all that stuff,” she says. “And then I started doing mathematics.” At that point, with the help of Simon Singh’s The Code Book, she realised the attraction was codebreaking rather than human languages themselves. Simultaneously, security and privacy were increasingly in the spotlight.

“I’m a very private person, and so privacy is near and dear to my heart,” she says. “It’s an important right that a lot of people don’t seem interested in exercising, but it’s still a right. Even if no one voted we would still agree that it was important for people to be able to vote.”

It was during her undergraduate years at Brown, which included a fifth-year Masters degree, that she made the transition from mathematics to cryptography and began studying computer science. She went on to do her PhD at the University of California at San Diego. Her appointment at UCL, which is shared between the Department of Computer Science and the Department of Crime Science, is her first job.

Probably her best-known work is A Fistful of Bitcoins: Characterizing Payments Among Men with No Names (PDF), written with Marjori Pomarole, Grant Jordan, Kirill Levchenko, Damon McCoy, Geoffrey M. Voelker, and Stefan Savage and presented at USENIX 2013, which studied the question of how much anonymity bitcoin really provides.

“The main thing I was trying to focus on in that paper is what bitcoin is used for,” she says. The work began with buying some bitcoin (in 2012, at about £3 each), and performing some transactions with them over a period of months. Using the data collected this way allowed her to uncover some “ground truth” data.

“We developed these clustering techniques to get down to single users and owners.” The result was that they could identify which addresses belonged to which exchanges and enabled them to get a view of what was going on in the network. “So we could say this many bitcoins passed through this exchange per month, or how many were going to underground services like Silk Road.”

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George Danezis – Smart grid privacy, peer-to-peer and social network security

“I work on technical aspects of privacy,” says George Danezis, a reader in security and privacy engineering at UCL and part of the Academic Centre of Excellence in Cyber Security Research (ACE-CSR). There are, of course, many other limitations: regulatory, policy, economic. But, he says, “Technology is the enabler for everything else – though you need everything else for it to be useful.” Danezis believes providing privacy at the technology level is particularly important as it seems clear that both regulation and the “moralising” approach (telling people the things they shouldn’t do) have failed.

https://www.youtube.com/watch?v=wAbKB0kaH6c

There are many reasons why someone gets interested in researching technical solutions to intractable problems. Sometimes the motivation is to eliminate a personal frustration; other times it’s simply a fascination with the technology itself. For Danezis, it began with other people.

“I discovered that a lot of the people around me could not use technology out of the box to do things personally or collectively.” For example, he saw NGOs defending human rights worry about sending an email or chatting online, particularly in countries hostile to their work. A second motivation had to do with timing: when he began work it wasn’t yet clear that the Internet would develop into a medium anyone could use freely to publish stories. That particular fear has abated, but other issues such as the need for anonymous communications and private data sharing are still with us.

“Without anonymity we can’t offer strong privacy,” he says.

Unlike many researchers, Danezis did not really grow up with computers. He spent his childhood in Greece and Belgium, and until he got Internet access at 16, “I had access only to the programming books I could find in an average Belgian bookshop. There wasn’t a BBC Micro in every school and it was difficult to find information. I had one teacher who taught me how to program in Logo, and no way of finding more information easily.” Then he arrived at Cambridge in 1997, and “discovered thousands of people who knew how to do crazy stuff with computers.”

Danezis’ key research question is, “What functionality can we achieve while still attaining a degree of hard privacy?” And the corollary: at what cost in complexity of engineering? “We can’t just say, let’s recreate the whole computer environment,” he said. “We need to evolve efficiently out of today’s situation.”

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Gianluca Stringhini – Cyber criminal operations and developing systems to defend against them

Gianluca Stringhini’s research focuses on studying cyber criminal operations and developing systems to defend against them.

Such operations tend to follow a common pattern. First the criminal operator lures a user into going to a Web site and tries to infect them with malware. Once infected, the user is joined to a botnet. From there, the user’s computer is instructed to perform malicious activities on the criminal’s behalf. Stringhini, whose UCL appointment is shared between the Department of Computer Science and the Department of Security and Crime Science, has studied all three of these stages.

https://www.youtube.com/watch?v=TY3wsqGOZ28

Stringhini, who is from Genoa, developed his interest in computer security at college: “I was doing the things that all college students are doing, hacking, and breaking into systems. I was always interested in understanding how computers work and how one could break them. I started playing in hacking competitions.”

At the beginning, these competitions were just for fun, but those efforts became more serious when he arrived in 2008 at UC Santa Barbara, which featured one of the world’s best hacking teams, a perennial top finisher in Defcon’s Capture the Flag competition. It was at Santa Barbara that his interest in cyber crime developed, particularly in botnets and the complexity and skill of the operations that created them. He picked the US after Christopher Kruegel, whom he knew by email, invited him to Santa Barbara for an internship. He liked it, so he stayed and did a PhD studying the way criminals use online services such as social networks

“Basically, the idea is that if you have an account that’s used by a cyber criminal it will be used differently than one used by a real person because they will have a different goal,” he says. “And so you can develop systems that learn about these differences and detect accounts that are misused.” Even if the attacker tries to make their behaviour closely resemble the user’s own, ultimately spreading malicious content isn’t something normal users intend to do, and the difference is detectable.

This idea and Stringhini’s resulting PhD research led to his most significant papers to date.

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MSc Information Security @UCL

As the next programme director of UCL’s MSc in Information Security, I have quickly realized that showcasing a group’s educational and teaching activities is no trivial task.

As academics, we learn over the years to make our research “accessible” to our funders, media outlets, blogs, and the likes. We are asked by the REF to explain why our research outputs should be considered world-leading and outstanding in their impacts. As security, privacy, and cryptography researchers, we repeatedly test our ability to talk to lawyers, bankers, entrepreneurs, and policy makers.

But how do you do good outreach when it comes to postgraduate education? Well, that’s a long-standing controversy. The Economist recently dedicated a long report on tertiary education and also discussed misaligned incentives in strategic decisions involving admissions, marketing, and rankings. Personally, I am particularly interested in exploring ways one can (attempt to) explain the value and relevance of a specialist masters programme in information security. What outlets can we rely on and how do we effectively engage, at the same time, current undergraduate students, young engineers, experienced professionals, and aspiring researchers? How can we shed light on our vision & mission to educate and train future information security experts?

So, together with my colleagues of UCL’s Information Security Group, I started toying with the idea of organizing events — both in the digital and the analog “world” — that could provide a better understanding of both our research and teaching activities. And I realized that, while difficult at first and certainly time-consuming, this is a noble, crucial, and exciting endeavor that deserves a broad discussion.

Information Security: Trends and Challenges

Thanks to the great work of Steve Marchant, Sean Taylor, and Samantha Webb (now known as the “S3 team” :-)), on March 31st, we held what I hope is the first of many MSc ISec Open Day events. We asked two of our friends in industry — Alec Muffet (Facebook Security Evangelist) and Dr Richard Gold (Lead Security Analyst at Digital Shadows and former Cisco cloud web security expert) — and two of our colleagues — Prof. Angela Sasse and Dr David Clark — to give short, provocative talks about what they believe trends and challenges in Information Security are. In fact, we even gave it a catchy name to the event: Information Security: Trends and Challenges.

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Introducing the expanded UCL Information Security Group

It takes quite a bit of institutional commitment and vision to build a strong computer security group. For this reason I am delighted to share here that UCL computer science has in 2014 hired three amazing new faculty members into the Information Security group, bringing the total to nine. Here is the line-up of the UCL Information Security group and teaching the MSc in Information Security:

Prof. M. Angela Sasse is the head of the Information Security Group and a world expert on usable security and privacy. Her research touches upon the intersection of security mechanisms or security policies and humans — mental models they have, the mistakes they make, and their accurate or false perceptions that lead to security systems working or failing.
Dr Jens Groth is a cryptographer renowned for his work on novel zero-knowledge proof systems (affectionately known as Groth-Sahai), robust mix systems for anonymous communications and electronic voting and succinct proofs of knowledge. These are crucial building blocks of modern privacy-friendly authentication and private computation protocols.
Dr Nicolas Courtois is a symmetric key cryptographer, known for pioneering work on algebraic cryptanalysis, extraordinary hacker of real-world cryptographic embedded systems, who has recently developed a keen interest in digital distributed currencies such as Bitcoin.
Prof. David Pym is both an expert on logic and verification, and also applies methods from economics to understand complex security systems and the decision making in organizations that deploy them. He uses stochastic processes, modeling and utility theory to understand the macro-economics of information security.
Dr Emiliano de Cristofaro researches privacy and applied cryptography. He has worked on very fast secure set intersection protocols, that are key ingredients of privacy technologies, and is one of the leading experts on protocols for privacy friendly genomics.
Dr George Danezis (me) researches privacy technologies, anonymous communications, traffic analysis, peer-to-peer security and smart metering security. I have lately developed an interest in applying machine learning techniques to problems in security such as anomaly detection and malware analysis.
Dr Steven Murdoch (new!) is an world expert on anonymous communications, through his association with the Tor project, banking security and designer of fielded banking authentication mechanisms. He is a media darling when it comes to explaining the problems of real-world deployed cryptographic systems in banking.
Dr Gianluca Stringhini (new!) is a rising star in network security, with a focus on the technical aspects of cyber-crime and cyber-criminal operations. He studies honest and malicious uses of major online services, such as social networks, email services and blogs, and develops techniques to detect and suppress malicious behavior.
Dr Sarah Meiklejohn (new!) has an amazing dual expertise in theoretical cryptography on the one hand, and digital currencies and security measurements on the other. She has developed techniques to trace stolen bitcoins, built cryptographic compilers, and contributed to fundamental advances in cryptography such as malleable proof systems.

One key difficulty when building a security group is balancing cohesion, to achieve critical mass, with diversity to cover a broad range of areas and ensuring wide expertise to benefit our students and research. I updated an interactive graph illustrating the structure of collaborations amongst the members of the Information Security Group, as well as their joint collaborators and publication venues. It is clear that all nine faculty members both share enough interest, and are complementary enough, to support each other.

Besides the nine full-time faculty members with a core focus on security, a number of other excellent colleagues at UCL have a track record of contributions in security, supporting teaching and research. Here is just a handful:

Prof. Brad Karp is an expert in networking and systems and has made seminal contributions to automatic worm detection and containment.
Dr David Clark specializes in software engineering with a core interest in information flow techniques for confidentiality, software security and lately malware.
Dr Earl Barr researches software engineering, and has researched security bugs, and malware as well as ideas for simple key management.
Prof. Ingemar Cox (part-time at UCL) is a world expert in multimedia security, watermarking and information hiding.
Prof. Yvo Desmedt (part-time at UCL) is a renowned cryptographer with key contributions in group key exchange, zero-knowledge and all fields of symmetric and asymmetric cryptography.

The full list of other colleagues working in security, including visiting researchers, post-doctoral researchers and research students list many more people – making UCL one of the largest research groups in Information Security in Europe.

This post originally appeared on Conspicuous Chatter, the blog of George Danezis.