July 12, 2020

Archives for March 2009

Fingerprinting Blank Paper Using Commodity Scanners

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.

Government Online: Outreach vs. Transparency

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.

Kundra Named As Federal CIO

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.