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Fingerprinting Blank Paper Using Commodity Scanners

March 13, 2009 by

Today Will Clarkson, Tim Weyrich, Adam Finkelstein, Nadia Heninger, Alex Halderman and I released a paper, Fingerprinting Blank Paper Using Commodity Scanners. The paper will appear in the Proceedings of the IEEE Symposium on Security and Privacy, in May 2009.

Here’s the paper’s abstract:

This paper presents a novel technique for authenticating physical documents based on random, naturally occurring imperfections in paper texture. We introduce a new method for measuring the three-dimensional surface of a page using only a commodity scanner and without modifying the document in any way. From this physical feature, we generate a concise fingerprint that uniquely identifies the document. Our technique is secure against counterfeiting and robust to harsh handling; it can be used even before any content is printed on a page. It has a wide range of applications, including detecting forged currency and tickets, authenticating passports, and halting counterfeit goods. Document identification could also be applied maliciously to de-anonymize printed surveys and to compromise the secrecy of paper ballots.

Viewed under a microscope, an ordinary piece of paper looks like this:

The microscope clearly shows individual wood fibers, laid down in a pattern that is unique to this piece of paper.

If you scan a piece of paper on an ordinary desktop scanner, it just looks white. But pick a small area of the paper, digitally enhance the contrast and expand the image, and you see something like this:

The light and dark areas you see are due to two factors: inherent color variation in the surface, and partial shadows cast by fibers in the paper surface. If you rotate the paper and scan again, the inherent color at each point will be the same, but the shadows will be different because the scanner’s light source will strike the paper from a different angle. These differences allow us to map out the tiny hills and valleys on the surface of the paper.

Here is a visualization of surface shape from one of our experiments:

This part of the paper had the word “sum” printed on it. You can clearly see the raised areas where toner was applied to the paper to make the letters. Around the letters you can see the background texture of the paper.

Computing the surface texture is only one part of the job. From the texture, you want to compute a concise, secure “fingerprint” which can survive ordinary wear and tear on the paper, such as crumpling, scribbling or printing, and moisture. You also want to understand how secure the technology will be in various applications. Our full paper addresses these issues too. The bottom-line result is a sort of unique fingerprint for each piece of paper, which can be determined using an ordinary desktop scanner.

For more information, see the project website or our research paper.

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Government Online: Outreach vs. Transparency

March 6, 2009 by

These days everybody in Washington seems to be jumping on the Twitter bandwagon. The latest jumpers are four House committees, according to Tech Daily Dose.

The committees, like a growing number of individual members’ offices, plan to use Twitter as a new tool to reach their audience and ensure transparency between the government and the public.

“I believe government works best when it is transparent and information is accessible to all….” [said a committee chair].

I’m all in favor of public officials using technology to communicate with us. But Twitter is a tool for outreach, not transparency.

Here’s the difference: outreach means government telling us what it wants us to hear; transparency means giving us the information that we, the citizens, want to get. An ideal government provides both outreach and transparency. Outreach lets officials share their knowledge about what is happening, and it lets them argue for particular policy choices — both of which are good. Transparency keeps government honest and responsive by helping us know what government is doing.

Twitter, with its one-way transmission of 140-character messages, may be useful for outreach, but it won’t give us transparency. So, Congressmembers: Thanks for Twittering, but please don’t forget about transparency.

(Interestingly, the students in my tech policy class were surprised to hear that any of the digerati had ever Twittered. The students think of Twitter as a tool for aging hepcat techno-poseurs. [Insert your own joke here.])

Meanwhile, the Obama team is having trouble transitioning its famous online outreach machinery into government, according to Jose Antonio Vargas’s story in the Washington Post:

WhiteHouse.gov, envisioned as the primary vehicle for President Obama to communicate with the online masses, has been overwhelmed by challenges that staffers did not foresee and technological problems they have yet to solve.

Obama, for example, would like to send out mass e-mail updates on presidential initiatives, but the White House does not have the technology in place to do so. The same goes for text messaging, another campaign staple.

Beyond the technological upgrades needed to enable text broadcasts, there are security and privacy rules to sort out involving the collection of cellphone numbers, according to Obama aides, who acknowledge being caught off guard by the strictures of government bureaucracy.

Here again we see a difference between outreach and transparency. Outreach, by its nature, must be directed by government. But transparency, which aims to offer citizens the information they want, is best embodied by vigorous activity outside of government, enabled by government providing free and open access to data. As we argued in our Invisible Hand paper, many things are inherently more difficult to do inside of government, so the key role of government is to enable a marketplace of ideas in the private sector, rather than doing the whole job.

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Kundra Named As Federal CIO

March 5, 2009 by

Today, the Obama administration named Vivek Kundra as the Chief Information Officer of the U.S. government, a newly created position.

This is great news. Kundra, in his previous role as CTO of the District of Columbia, made great strides in opening the DC government by publishing government data. When he spoke at our Thursday Forum last fall, everyone was impressed by how quickly and effectively he had transformed the DC government’s approach to technology.

First, he set up an open Data Catalog, where lots of data collected by the DC government is freely available in standard formats. Second, he ran the Apps for Democracy contest, in which he challenged citizens to develop applications to take advantage of all the data that the DC government is publishing. The results were impressive—with 47 different apps submitted by citizens—and also inexpensive.

Most impressively, in doing this he overcame the natural inertia of big city government. The Federal government will be even harder to budge, but with the right support from the top, Kundra could bring a new level of openness and tech-friendliness to the government.

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New Podcast: CITP Conversations

March 3, 2009 by

Over the last few months, as the pace of activity at CITP has increased, we’ve fielded a growing number of requests from points around the web, and around the world, for podcasts and other ways to “attend” our events virtually. We hear you, and we’re working on it.

Today, I’m very pleased to announce a new CITP podcast, which will carry audio of some of our events as well as brief conversations recorded expressly for the podcast feed. Currently, those conversations include one with Paul Ohm on Net Neutrality and the Wiretap Act, and another with Ed on “Rebooting our Cyber-Security Policy,” drawing on the themes of his recent Thursday Forum talk.

We are also working to offer more of our events in video formats, and we remain open to exploring additional options. Stay tuned!

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RIP Rocky Mountain News

March 2, 2009 by

The Rocky Morning News, Colorado’s oldest newspaper, closed its doors Friday. On their front page they have this incredibly touching video:

Final Edition from Matthew Roberts on Vimeo.

The closing of a large institution like a daily newspaper is an incredibly sad event, and my heart goes out to all the people who suddenly find their lives upended by sudden unemployment. Many talented and dedicated employees lost their jobs today, and some of them will have to scramble to salvage their careers and support their families. The video does a great job of capturing the shock and sadness that the employees of the paper feel—not just because they lost their jobs, but also because in some sense they’re losing their life’s work.

With that said, I do think it’s unfortunate that part of the video was spent badmouthing people, like me, who don’t subscribe to newspapers. One gets the impression that newspapers are failing because kids these days are so obsessed with swapping gossip on MySpace that they’ve stopped reading “real” news. No doubt, some people fit that description, but I think the more common case is something like the opposite: those of us with the most voracious appetite for news have learned that newsprint simply can’t compete with the web for breadth, depth, or timeliness. When I pick up a newspaper, I’m struck by how limited it is: the stories are 12 to 36 hours old, the range of topics covered is fairly narrow, and there’s no way to dig deeper on the stories that interest me most. That’s not the fault of the newspaper’s editors and reporters; newsprint is just an inherently limited medium.

As more newspapers go out of business in the coming years, I think it’s important that our sympathy for individual employees not translate into the fetishization of newsprint as a medium. And it’s especially important that we not confuse newsprint as a medium with journalism as a profession. Newsprint and journalism have been strongly associated in the past, but this an accident of technology, not something inherent to journalism. Journalism—the process of gathering, summarizing, and disseminating information about current events—has been greatly enriched by the Internet. Journalists have vastly more tools available for gathering the news, and much more flexible tools for disseminating it. The replacement of static newspapers with dynamic web pages is progress.

But that doesn’t mean it’s not a painful process. The web’s advantages are no consolation for Rocky employees who have spent their careers building skills connected to a declining technology. And the technical superiority of web will be of little consolation to Denver area readers who will, in the short run, have less news and information available about their local communities. So my thoughts and sympathy today are with the employees of the Rocky Mountain News.

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