Last Updated: July 2017

Special Issue of Journal of Computer Security on Verified Information Flow Security

I'm very happy to announce that the Special Issue on Verified Information Flow Security of the Journal of Computer Security (Volume 25, issue 4-5) has just been published. For this special issue I was honoured to act as Guest Editor alongside Andrei Sabelfeld and Lujo Bauer. If you're interested in what kinds of security guarantees can be provided by platform enforced (and often formally verified) information flow control, this special issue is a good place to start, covering practical systems from new hardware architectures and hypervisors to new programming languages and distributed systems. You can read more about the special issue and its contents in the freely-available foreword [Journal of Computer Security, Guest Editorial pdf].

CDDC wins 3 SA iAwards

I'm honoured to be a part of the team behind the Cross Domain Desktop Compositor (CDDC) [Annual Computer Security Applications Conference (ACSAC) 2016 pdf], which last night won three SA iAwards. The CDDC was named the South Australian:

  • Research and Development Project of the Year,
  • Infrastructure and Platforms Innovation of the Year, and
  • Public Sector and Government Markets winner.

The CDDC is a joint collaboration between Data61 and DST Group that Kevin Elphinstone and I, in our Data61 capacities, established with Mark Beaumont and Chris North of DST Group's Active Security Technologies Group. Massive credit to Mark Beaumont who conceived much of the CDDC's original design, for whom this marks his second success at the iAwards after a win in 2014 with the Digital Video Guard.

You can read more about the CDDC and the win on our official blog post.

CDDC SA iAwards

I'm Hiring a Researcher (postdoc or graduate) in Program Verification and Security

'm currently recruiting a researcher to work on the application of concurrent separation logic for verifying information flow security of seL4-based, security-critical embedded systems. Verified information flow security has seen something of a renaissance over the past 5 years, with success stories such as seL4 or the more recent mCertiKOS; but concurrency remains an open challenge and one that this project aims to address for the first time.

Click here for more information.

About Me

I am a Lecturer in the School of Computing and Information Systems of the University of Melbourne. Prior to joining Melbourne in May 2016, I was employed in the Software Systems Research Group of NICTA (now Data61), and was a Conjoint Senior Lecturer in the school of Computer Science and Engineering of UNSW. I joined NICTA and UNSW in 2010 from Oxford, where I completed a D.Phil. (PhD) in Computer Science, awarded in 2011. Before moving to Oxford, I worked for the Defence Science and Technology Organisation after my undergraduate study at the University of Adelaide.

I live in Melbourne with my wife and two children, breathe (and sometimes write) alternative music, and spend too much time on Twitter engaging a hot-cold obsession with Australian politics, security and privacy. I love great ales, informed by my days in Oxford, and rich reds, like any Adelaide native.

Research and Collaborations

My research is focused on the problem of how to build highly secure computing systems cost-effectively. As part of this, I lead Data61's work on proving computer software and systems secure, and am leading or otherwise involved in a number of projects as part of Data61's Trustworthy Systems activity, as detailed on my Data61 page. Below are listed my current active areas of research and collaboration. My interest in security, and belief about the best ways to build secure systems more effectively, is very broad. Thus I tend to collaborate across various disciplines including Software Engineering, Systems, Hardware Security, Formal Methods, Programming Languages and Human Factors.

Information Flow   One of the biggest challenges faced in security today is how to ensure that computer systems can keep their secrets from well-motivated adversaries — just think of how many news stories you've read about personal information having been stolen and publicised by attackers. For this reason, a large part of my research has investigated how to guarantee the absence of unwanted information leaks in computer software and systems. I led the team that completed the world's first proof [IEEE Symposium on Security and Privacy ("Oakland" S&P) 2013 pdf] of information flow security for a general-purpose operating system kernel, seL4, which you can read more about on the Information Flow project page. This proof, along with subsequent work, guarantees that seL4 will prevent all unwanted information leaks up to timing channels, i.e. that it is free of unwanted storage channels.

My current work in this space aims to understand how to verify information flow security for concurrent programs (like those that run on top of seL4), and how to compile such programs while making sure they still preserve their security guarantees. So far, we have developed an initial framework for exploring these questions [IEEE Computer Security Foundations Symposium (CSF) 2016 ], which is publicly available in the Archive of Formal Proofs (AFP) as the two AFP entries:

Timing Channels   Timing channels leak information (whether intentionally or not) to an adversary who can observe differences in the relative timing of different events. Unlike for storage channels, we are not yet able to prove the absence of timing channels in systems, largely because many timing channels exploit the timing properties of hardware microarchitectural features, like caches, which are not even documented, so are very difficult to reason about formally. For this reason, these channels must be dealt with empirically. I have been involved in NICTA's Timing and Side Channels activity, where we pioneered new techniques for empirically measuring the effectiveness of various timing channel mitigation techniques for seL4 [ACM Conference on Computer and Communications Security (CCS) 2014 pdf].

Cost-Effective Verified Systems via Verifying DSLs   While security proofs, like those for seL4 that I have led, can give extremely high levels of assurance for security-critical systems, they remain relatively expensive to perform. Much of my recent research has therefore focused on how to reduce the cost of verifying properties of systems software. One technique I have explored, in collaboration with Programming Languages researchers from UNSW (notably Gabi Keller) via NICTA's Cogent project, has been to write verified systems software in a Domain Specific Language (DSL). Cogent [International Conference on Functional Programming (ICFP) 2016 pdf] is a programming language that is carefully designed to enable systems written in it to be cheaply proved correct. It is coupled with a verifying compiler [International Conference on Interactive Theorem Proving (ITP) 2016 pdf] that automatically proves that the compiled code implements the Cogent source semantics. In conjunction with my PhD students Sidney Amani and Liam O'Connor (co-supervised with Gabi Keller), my undergraduate thesis student Japheth Lim, and the rest of the Cogent team, we have used this technique to build and (partially) formally verify correct Linux file systems far more cheaply than e.g. the verification for the seL4 kernel [International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS) 2016 html].

Proof Cost Estimation   The effort required to verify software as being secure is an obvious barrier to its wide adoption. But just as important is the inability of software engineering managers to be able to predict the costs (and associated benefits) of proving their software correct. Another of my recent research activities has been to investigate this question in the context of NICTA's Proof, Measurement and Estimation (PME) project. As part of this work, my PhD student Daniel Matichuk and I, in collaboration with Empirical Software Engineering researchers and NICTA's PME team, explored the relationship between the size of a statement to be proved about a piece of software, and the amount of effort required to prove the statement (using as a proxy the number of lines required to write the proof, which we had already established [ACM/IEEE Symposium on Empirical Software Engineering and Measurement (ESEM) 2014 pdf] is strongly linearly related). To do so, we crunched historical data about the various seL4 proofs as well as some other large, publicly available software proofs. We established empirically for the first time [International Conference on Software Engineering (ICSE) 2015 pdf] that a consistent relationship exists here and that it is in fact quadratic. This work is the first step towards building a predictive model for estimating the level of effort required to verify a piece of software.

Proof Automation   Besides writing verified software in custom DSLs leveraging verifying compilation to dramatically ease the cost of formally verifying secure systems, another more direct approach I have investigated with my PhD student Daniel Matichuk has been to develop languages in which custom, automatic proof tactics can be written for the Isabelle proof assistant. Daniel designed and developed Eisbach [International Conference on Interactive Theorem Proving (ITP) 2014 pdf, Journal of Automated Reasoning (to appear)] the first such language that integrates with Isabelle's high-level notation for writing (structured) proofs, and so requires no knowledge of Isabelle's internals, making it usable by relative novices.

Highly-Secure and Usable, Verified Cross Domain Systems   All of the above research is aimed towards being able to build extremely secure systems — and to demonstrate via rigorous evidence that they are indeed so — at reasonable cost. I am currently leading, alongside Kevin Elphinstone, a collaboration with the Defence Science and Technology Group (DST Group), in which we are building and formally verifying as secure a clever Cross-Domain device called the Cross Domain Desktop Compositor (CDDC) [Annual Computer Security Applications Conference (ACSAC) 2016 pdf]. The CDDC allows users to interact with both highly-classified and lower-classification networks from a single display (monitor), keyboard and mouse. Its design makes it far more secure than existing solutions while also offering much greater usability, showing that with clever design usability and security need not be in conflict. We are currently working on building and verifying an seL4-based implementation of the device, leveraging our current work on verified information flow security.

Usable Security   As part of my work on building and verifying cross domain systems, I am also investigating how issues of usability and security, including human cognition and perception, interact with the process of formally proving a system secure. While still in its very early stages, this has so far seen me engaging with some of Australia's leading researchers in Psychology and Human Decision Making.

Reasoning about Capability-Based Software   Continuing the work I began during my D.Phil. (PhD), where I investigated [thesis pdf] techniques to formally reason about the security of capability-based security-enforcing software abstractions, I am currently collaborating with researchers from Imperial College London, Victoria University Wellington and Google on techniques for formally reasoning about risk and trust (including the absence of such) for capability-based software.

Working with Me

I'm always looking for motivated students to work with. Check out my page for prospective research students.


Google Scholar has a fairly complete list of my publications. You can also try my entry on DBLP, which may not be quite so complete.


In 2017, I am currently teaching:

I have previously taught:

And before that, at UNSW:

I have also taught half-day courses to industry on topics including:

If your company develops software and would like to know how you can more easily detect and remove bugs during development, and would like to know more, please get in touch.


Current PhD students:

Previous research students:


I serve, and have served, on a range of Program Committees, listed below. I am also editing a special issue of the Journal of Computer Security, and serving as a member of the Technical Community that developed the Protection Profile for General Purpose Operating Systems v4.0 (released August 2015).

Program Committees