How About Some Raspberry Pi?

February 29, 2012

The BBC News site reports today that the Raspberry Pi Foundation has announced that its Model B credit-card-sized computer has gone on sale. for £22 ($35).  (CNN also has a story on the launch.)

The Raspberry Pi is a bare-bones, low-cost computer created by volunteers mostly drawn from academia and the UK tech industry.

Sold uncased without keyboard or monitor, the Pi has drawn interest from educators and enthusiasts.

The Model B board mounts a CPU, GPU, 256 MB of memory, audio, HDMI, and RCA video outputs. an Ethernet connection, and two USB ports; there is also a slot for an SD memory card.  It runs the Linux operating system, and is powered by a USB power supply, similar to those used to charge cell phones.

The idea behind the Raspberry Pi is to provide a cheap computer that can be used in quantity, particularly in educational settings.  A slightly less capable Model A (with reduced connectivity) will go on sale shortly for £ 16 ($25). The initial launch of the Model B is aimed at developers and evaluators:

This first launch is aimed at software and hardware enthusiasts, makers, teachers and others who want to build exciting things with the Raspberry Pi before the official educational launch, which will happen later in 2012.

The Pi is being offered initially through two UK distributors, Premier Farnell and RS Components.  The initial stock of Model B  units sold out within a few hours; demand was so high that at least one of the distributors’ web sites crashed under the load.

Once the dust settles, I may just have to get one of these.


Interview with Bruce Schneier

February 28, 2012

I’ve mentioned Bruce Schneier, and his blog, Schneier on Security, a number of times in discussing various security issues (and there is always a link to his blog in the sidebar).  He is one of the most thoughtful observers of the security scene, and is the author of several books, including Applied Cryptography, Secrets and Lies, and Beyond Fear (all of which, by the way, I recommend highly).  He has just posted the text of a recent interview related to his latest book, Liars and Outliers.  The interview, which first appeared at “The Browser”, is interesting because it includes brief discussions of five other books, chosen by Schneier, that are related to his theme of “trust”:

  • The Penguin and the Leviathan, by Yochai Benkler 
  • The Folly of Fools, by Robert Trivers
  • The Murderer Next Door, by David M. Buss
  • The Better Angels of Our Nature, by Steven Pinker
  • Braintrust, by Patricia S. Churchland

Schneier points out that we live in a society that could not possibly exist without a great deal of trust.

Security exists to facilitate trust. Trust is the goal, and security is how we enable it. Think of it this way: As members of modern society, we need to trust all sorts of people, institutions and systems. We have to trust that they’ll treat us honestly, won’t take advantage of us and so on – in short, that they’ll behave in a trustworthy manner.

Trust has always been a fundamental part of human society.  What is somewhat different today is the extent and complexity of our trust relationships, and the degree to which they are intertwined via technology.

Today we need to trust more people than ever before, further away – whether politically, ethnically or socially – than ever before. We need to trust larger corporations, more diverse institutions and more complicated systems. We need to trust via computer networks. This all makes trust, and inducing trust, harder.

He explains that his chief concerns about privacy and security are not about organized crime or terrorism; societal pressures do a fairly good job of ensuring they exist only at the margins of society.  He believes a bigger danger is that we will get the rules wrong when we try to deal with large, legitimate, powerful entities.

The global financial crisis was not a result of criminals, it was perpetrated by legitimate financial institutions pursuing their own self-interest. The major threats against our privacy are not from criminals, they’re from corporations trying to more accurately target advertising. The most significant threat to the freedom of the Internet is from large entertainment companies, in their misguided attempt to stop piracy. And the cyberwar rhetoric is likely to cause more damage to the Internet than criminals could ever dream of.

Getting these trade-offs wrong has the potential to cause serious damage.

The whole interview is well worth a read, and the books he selected sound most interesting, too.

LibreOffice 3.5 is Available

February 27, 2012

As readers may recall, back in September 2010, the LibreOffice project was created as a fork of the existing OpenOffice project, to continue development of the productivity suite separately from Oracle.   The Document Foundation was set up to be the governing body for LibreOffice, much as the Mozilla Foundation oversees the development of Firefox, Thunderbird, and other projects.  LibreOffice is free (as in beer) to download, and is released under the GNU Lesser General Public License [LGPL], version 3.

The foundation has now announced the release of version 3.5 of LibreOffice, for Windows, Mac (Intel or PowerPC), and Linux.   It incorporates many security and bug fixes, as well as some new features, including:

  • An import filter for Microsoft Visio documents
  • Better font “hinting”
  • Automatic check for updates
  • Native PostgreSQL database driver
  • User interface improvements

The foundation’s site has a more complete overview of new features and fixes, as well as the Release Notes.  You can download the new version here.

As with previous versions of LibreOffice and OpenOffice, the software is able to read documents in many proprietary formats, including Microsoft Office formats, and can save documents in many of them.  It has also had, for years, the ability to save documents in Adobe’s Portable Document Format (.pdf), making them accessible on many different platforms.

Incidentally, The Document Foundation has now been legally incorporated in Berlin, Germany, as a rechtsfähige Stiftung des bürgerlichen Rechts, a German endowed not-for-profit foundation.

(Mea culpa: The 3.5 release was made on February 14.  It was on my list of things to blog, but somehow slipped through the cracks.)


Open Source for Research

February 26, 2012

One of the important principles of the scientific method is the full reporting of experimental results: not just the researcher’s conclusions, but also a detailed description of the method and apparatus used, and of the data obtained.  The idea is to enable others to replicate the experiment, to help ensure that the results are not a fluke, or just a mistake.  Ars Technica reports on a new proposal, published in an editorial in the journal Nature, to provide open source code for the computations that underlie most contemporary scientific papers.

Reproducibility refers to the ability to repeat some work and obtain similar results.  …  Scientific papers include detailed descriptions of experimental methods—sometimes down to the specific equipment used—so that others can independently verify results and build upon the work.

Reproducibility becomes more difficult when results rely on software. The authors of the editorial argue that, unless research code is open sourced, reproducing results on different software/hardware configurations is impossible.

If one accepts the fundamental idea of full disclosure, it is hard to argue with the basic thrust of this proposal.  It is a rare piece of experimental research that does not involve the use of some software to process and analyze the resulting data.  At present, there are some journals, such as Science, which expect code to be included as part of a submitted paper.  Others, such as Nature itself, only require a detailed written description of the code.  In some cases, the authors offer to supply an executable (binary) version of the code on request.

Alternatives to the actual source code are less than entirely satisfactory for a number of reasons.  Any experienced software developer can tell you that a major problem with software documentation (that is, a description of the program) is that the description does not match what the program actually does.  Executable versions of a program will generally  be usable only for others with the same computing platform, and are largely opaque; if someone attempts to replicate the results, but gets different answers, it is hard to know where to look.  As I’ve noted before, software for numerical analysis is especially subject to errors resulting from the idiosyncracies of computer arithmetic; to make matters worse, these effects can be platform-dependent.   Even with source code available, there can be ambiguities in the order in which arithmetic operations are performed; there is seldom any guaranty that the order will match the conventional order expected from looking at the mathematics.

Of course, there are in some cases obstacles to releasing the source code.  But the purpose of the scientific enterprise really requires every effort to make experimental results as transparent as possible.


A Fascinating Letter, continued

February 24, 2012

A couple of days ago, I wrote about some newly-declassified correspondence between  the US National Security Agency and John Nash, the mathematician who won a Nobel Prize in Economics for his work on game theory, and was the subject of the book, and movie, A Beautiful Mind.

I’ve subsequently come across a couple of other blog posts on this.  At the Turing’s Invisible Hand blog, Noam Nisan reviews the similarity of what Nash was suggesting, and the modern approach to cryptography.  He has some additional quotes from Nash’s letters, too.

At the Adventures in Computation blog, Aaron (who in real life is an Assistant Professor of Computer Science at the University of Pennsylvania) mentions another, slightly later letter that also foreshadows modern ideas about computational complexity.  This letter was written in March, 1956, (originally in German) by  Kurt Gödel, the Austrian mathematician  best known for his Incompleteness Theorem, to John von Neumann, the Hungarian-American mathematician who (among many other things) worked on the Manhattan Project, and in the fields of game theory, quantum mechanics, and computer science.  Sadly, not much came of the letter; von Neumann was suffering from cancer, possibly caused by radiation exposure he received while working on the atomic bomb.

Both Gödel and von Neumann spent time in Princeton, at the Institute for Advanced Study, and Nash spent much of his career at Princeton University.  Nisan has a somehow appealing suggestion:

That both Nash and Goedel passed through Princeton may imply that these ideas were somehow “in the air” there.

Perhaps the idea of something in  the air is too fanciful, but there was quite a confluence of very bright people in Princeton (including Einstein, of course).  I guess it would be surprising if nothing of note had come from it.

GPS Jamming in the UK

February 23, 2012

Just recently, we have seen the Federal Communications Commission [FCC] suspend indefinitely its provisional approval of a new wireless broadband Internet service, proposed by LightSquared, because of concerns about potential interference with the Global Positioning System [GPS].  As I’ve noted before, the GPS is used for much more than those little direction-finding gizmos in your car.   Besides the potential problems associated with large new deployments, like the proposed LightSquared system, there is an ongoing problem with deliberate jamming of GPS signals.

Jamming GPS signals is not technically difficult.  The signals are coming from satellites ~20,000 km away, and the radiated power is ~ 100 watts, not much more than a typical terrestrial cell phone tower.    (By way of comparison, LightSquared’s proposed ground stations would  each have radiated ~15,000 watts .)  So GPS devices must be able to receive  very weak signals, which means that generating enough “static” to mask the desired signal does not take a very large or powerful transmitter.

Some new research, summarized in an article at New Scientist, surveyed the incidence of GPS jamming in the UK since September of last year.  The research, carried out by a group organized by the Government’s Technology Strategy Board [TSB]. and led by Chronos Technology,  found that jamming is a very real problem.

A secret network of 20 roadside listening stations across the UK has confirmed that criminals are attempting to jam GPS signals on a regular basis, a conference at the National Physical Laboratory, in London, will hear later today. Set up by the government’s Technology Strategy Board (TSB) and run by Chronos Technology of the Forest of Dean, UK, the Sentinel network has sensed an average of ten jamming incidents per month since September 2011.

The results, which are being presented this week at a conference sponsored by the TSB, indicate that GPS jamming takes place ~10 times per month at the monitored locations.  (BBC News also has an article on this research.)  In many countries (including, I believe, the UK) the sale or use  of GPS jamming equipment is illegal.   Nonetheless. it seems to be easily available via the Internet.

One prime suspect in the investigation so far is the trucking industry.  GPS devices are used widely: in some cases, to track vehicle movements in order to assess tolls; in other cases, to keep tabs on the vehicle drivers.  These situations obviously have significant potential motives for jamming.  The New Scientist suggests another possible reason, based on the ability of a good GPS system to give directions “off the beaten track””

Vigilantes could be one source: a major problem with GPS is the way some small villages and towns suffer visits from dangerously outsized trucks – which often get stuck in tiny streets – attempting to follow satnav-advised shortcuts. So it is possible locals are placing jammers to prevent drivers’ antisocial behaviour.

I hope these results will stimulate more work on jamming prevention, from both the technical and legal viewpoints.  As I’ve said in the LightSquared case, GPS technology is just too useful, in too many ways, to be compromised because of carelessness.

A Fascinating Letter

February 22, 2012

I’ve mentioned here before the close connection between mathematics and cryptography, especially the public key cryptography that is used, among other things, as the basis for the SSL/TLS protocols that secure Internet commerce.   The security of the system depends on the use of a “one way” function; that is, a function that is easy to compute, but whose inverse is very difficult to compute.  For example, finding the product of two large prime numbers is relatively easy, but factoring the resulting product to find the original primes is believed to be computationally infeasible, provided the numbers are large:  2048 bits or more.  The analysis of the minimum effort required to solve problems like this is the focus of computational complexity theory, which emerged in the 1960s and 1970s as the merger of ideas from computer science and mathematics.

The New Scientist reports that the  US National Security Agency [NSA] has recently declassified some fascinating correspondence [PDF], centering on a letter it received from John Nash in 1955, on the subject of encryption systems.  Readers may recognize the name; John Nash was the brilliant mathematician and game theorist, subject of Sylvia Nasar’s  1998 biography, A Beautiful Mind, and the 2001 film  of the same name.  He made very important contributions to game theory, especially, and was one of the winners of the 1994 Nobel Memorial Economics Prize on the basis of that work.  Unfortunately, as related in the biography, he struggled with schizophrenia most of his adult life.

Apparently, Nash had written to predecessor agencies of the NSA (formed in 1952) back in 1950, describing a cipher machine he had designed.  The 1955 letter was an attempt to re-start that conversation.  The letter, written in longhand, appears at first glance more like something written by a high-school student (with not very good penmanship), rather than by one of the most brilliant living mathematicians.  It has a fair sprinkling of misspelled and crossed-out words.  Nash himself writes:

I hope my handwriting, etc. do not give the impression I am just a crank or circle-squarer.  My position here is Assist. Prof. of Math.  My best known work is in game theory (reprint sent separately).

(He was at MIT at the time, although he subsequently spent most of his time at Princeton.  It is also somewhat amusing that the reprint, enclosed almost as an afterthought, was of the work that won a Nobel Prize.)

What is striking about the letter is that Nash anticipates the core of computational complexity, a decade or two before it made a public appearance.  He proposes that the security of an encryption system is founded on the difficulty of the computation required to break it.

So a logical way to classify enciphering processes is by the way in which the computation length for the computation of the key increases with increasing length of the key. This is at best exponential and at worst probably at most a relatively small power of r, ar2, or ar3, as in substitution ciphers.

He conjectures that, with a sufficiently complex encryption function, the computation can be made of exponential difficulty.  Why does this matter?  He explains that, if the computation is difficult enough, the encryption can be made extremely secure as long as the key is long enough.

The significance of this general conjecture, assuming its truth, is easy to see.  It means that it is quite feasible to design ciphers that are effectively unbreakable.

He says that he can’t prove the conjecture, and in fact expresses doubt that it is provable.  (So far, he’s right about that.)  But it seems clear that he grasped the essence of the problem quite a while before it was generally realized.  I was very glad when I heard that he had won the Nobel Prize; he did not have an easy life, and his contributions deserved recognition.  I’m similarly glad to see this work emerge from the shadows.

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