Monthly Archives: May 2013

A further observation on quantum computing

Today we’ve published a paper showing that Bell’s inequality is violated in fluid mechanics. What has this to do with computing or security? Well, when we posted a paper back in February pointing out that hydrodynamic models of quantum physics raise questions about the scalability of quantum computing, a number of people asked for a better explanation of how this squares with the Bell tests. John Bell proved an inequality in 1964 that applies to classical particles but that is broken by quantum mechanical ones. In today’s paper we show that Bell’s inequality does not hold in classical fluid dynamics, as angular momentum and energy are delocalised in the fluid.

This may have implications for engineering, science and philosophy. On the engineering front, nine-figure sums have been poured into developing quantum computers, but even advocates of quantum computing admit they don’t really work. As our February paper argued, a hydrodynamic interpretation of quantum mechanics may suggest reasons why.

On the scientific front, the Bell tests are commonly seen as excluding not just local hidden-variable models of quantum mechanics, but local realism too. Our paper shows that the two are distinct, and thus leaves more room for research on quantum foundations. It also shows that we should be more careful in our use of terms such as ‘local’ – which might be of interest to the philosophers; the Bell tests do not draw quite as clear a dividing line between the quantum and classical worlds as many have believed.

Revisiting secure introduction via hyperlinks

Today at W2SP I presentednew paper making the case for distributing security policy in hyperlinks. The basic idea is old, but I think the time is right to re-examine it. After the DigiNotar debacle, the community is getting serious about fixing PKI on the web. It was hot topic at this week’s IEEE Security & Privacy (Oakland), highlighted by Jeremy Clark and Paul van Oorschot’s excellent survey paper. There are a slew of protocols under development like key pinning (HPKP), Certificate Transparency, TACK, and others. To these I add s-links, a complementary mechanism to declare support for new proposals in HTML links. Continue reading Revisiting secure introduction via hyperlinks

A search engine for code

In a seminar today, we will unveil Rendezvous, a search engine for code. Built by Wei-Ming Khoo, it will analyse an unknown binary, parse it into functions, index them, and compare them with a library of code harvested from open-source projects.

As time goes on, the programs we need to reverse engineer get ever larger, so we need better tools. Yet most code nowadays is not written from scratch, but cut and pasted. Programmers are not an order of magnitude more efficient than a generation ago; it’s just that we have more and better libraries to draw on nowadays, and a growing shared heritage of open software. So our idea is to reframe the decompilation problem as a search problem, and harness search-engine technology to the task.

As with a text search engine, Rendezvous uses a number of different techniques to index a target binary, some of which are described in this paper, along with the main engineering problems. As well as reverse engineering suspicious binaries, code search engines could be used for many other purposes such as monitoring GPL compliance, plagiarism detection, and quality control. On the dark side, code search can be used to find new instances of disclosed vulnerabilities. Every responsible software vendor or security auditor should build one. If you’re curious, here is the demo.

Traceability in the Queen's Speech

The Queen’s speech at today’s state opening of Parliament includes the prediction:

“In relation to the problem of matching Internet protocol addresses, my Government will bring forward proposals to enable the protection of the public and the investigation of crime in cyberspace”

This is all that remains of the Home Office’s ambition to bring forward a revised version of the Draft Communications Data Bill that two Parliamentary Select Committees were so unimpressed by, and which the Liberal Democrats have declined to support.

The sole issue on which there appears to be political consensus is that “something must be done” about the traceability failure that regularly occurs when the Internet is accessed from a smartphone. The shortage of IPv4 addresses means that the mobile companies cannot give each smartphone a unique IP address — so hundreds of users share the same IP address with only the TCP/UDP source port number distinguishing their traffic. Because this sharing is done very dynamically the mobile phone companies find it problematic to record the source port mapping, and they have argued that the way the EU Data Retention Directive is written they have no obligation to make and keep such records.

I wrote about this issue at some length on this blog in January 2010, although until very recently the Home Office considered it to be tantamount to a state secret and were extremely coy about discussing it in the public.

The Queen’s “bring forward proposals” phrase appears to cover a range of options:

  • the mobile companies decide that they can manage to log the source port mapping data after all;
  • the Home Office pays for new kit at the mobile companies that will allow source port mapping to be done;
  • there is a short bill (or clause in another bill) that requires the logging to be done (this might avoid any question of payments being ultra vires, or would ensure compliance by companies (possibly broadband suppliers) that looked like becoming stragglers;
  • there are discussions but nothing happens at all — perhaps because the tide turns against Data Retention as being a necessary and proportionate policy. A number of other EU countries have found it to be incompatible with fundamental human rights.

The Open Rights Group (ORG) have recently produced a pamphlet (available online here) setting out how surveillance might be better approached in this century. I contributed the chapter on the technical issues…

… if you don’t have time to read the whole thing then the New Statesman has an edited version of my chapter; and you can watch a short video of myself (and two other contributors) explaining the major issues.