November 24, 2020

Archives for November 2004

EFF Names Advisory Board

The Electronic Frontier Foundation has named its first advisory board. I’m on it, along with Michael Froomkin, Paul Grewal, Jim Griffin, David Hayes, Mitch Kapor, Mark Lemley, Eben Moglen, Deirdre Mulligan, Michael Page, Michael Traynor, and Jim Tyre.

Identification Codes on Printer Output

A Xerox engineer says that color printers from Xerox and other companies print faint information in the background of printed-out pages, to identify the model and serial number of the printer that printed the pages. According to a story, the information is represented as a set of very small yellow dots. (We already knew that some printers did this. The article tells us more about how it’s done.)

We have a Xerox color printer here (a Phaser 860). We tried printing out a page and looking for the dots, but we couldn’t find them, even with the aid of a magnifying glass and blue LED light. If anybody can find the dots on their output, please let me know.

There are still several unanswered questions about this scheme:

Do they use encryption, and if so, how? Even if we can find the dots and read out the digital bits they represent, we may not be able to tell what information those bits are encoding. They might be putting the model and serial number onto the page in such a way that we can learn to read them. Or perhaps they are encrypting the information so that we can’t read out the identifying information but we can at least recognize whether two pages were printed on the same printer. Or perhaps they encrypt the information so that we can’t tell anything without having some secret key.

If there is a secret key, who knows it? The key might be disclosed to the government so that they can extract the model and serial number from a page at will. (And if the U.S. government has the key, which other governments do?) Or the key might be known only to the printer vendor, so that the government needs the vendor’s help to decode the dots. If they use public-key cryptography, then the decoding key might be known only to the government and not to the printer vendor.

Do they try to track who buys each printer? If they can extract the serial number, they might want to know who has that printer. They could try to track the passage of each individual printer through the supply chain, to get an idea of who might have bought it. They might also build a database of information gleaned through service calls and warranty registrations.

What we know already is enough to make privacy advocates itchy. It’s probably possible to design a system that raises fewer privacy issues, while still allowing certain limited use of printer-specific marks as courtroom evidence. For example, one could build a system so that somebody who has physical possession of a printer, and physical possession of a printed page, and access to a special crypto key, can tell whether or not that page was printed by that printer, but can’t learn anything else.

New Study of E-Voting Effects in Florida

Yesterday, a team of social scientists from UC Berkeley released a study of the effect of e-voting on county-by-county vote totals in Florida and Ohio in the recent election. It’s the first study to use proper social-science modeling methods to evaluate the effect of e-voting.

The study found counties with e-voting tended to tilt toward Bush, even after controlling for differences between counties including past voting history, income, percentage of Hispanic voters, voter turnout, and county size. The researchers estimate that e-voting caused a swing in favor of Bush of up to 260,000 votes in Florida. (A change of that many votes would not be enough to change the election’s result; Bush won Florida by about 350,000 votes.)

No e-voting effect was found in Ohio.

The study looks plausible, but I don’t have the expertise to do a really careful critique. Readers who do are invited to critique the study in the comments section.

Regardless of whether it is ultimately found credible, this study is an important step forward in the discourse about this topic. Previous analyses had shown differences, but had not controlled for the past political preferences of individual counties. Skeptics had claimed that “Dixiecrat” counties, in which many voters were registered as Democrats but habitually voted Republican, could explain the discrepancies. This study shows, at least, that the simple Dixiecrat theory is not enough to refute the claim that e-voting changed the results.

Assuming that the study’s authors did their arithmetic right, there are two possibilities. It could be that some other factor, beyond the ones that the study controlled for, can explain the discrepancies. If this is the case, we can assume somebody will show up with another study demonstrating that.

Or it could be that e-voting really did affect the result. If so, there are several ways this could have happened. One possibility is that the machines were maliciously programmed or otherwise compromised; I think this is unlikely but unfortunately the machines are designed in a way that makes this very hard to check. Or perhaps the machines made errors that tended to flip some votes from one candidate to the other. Even random errors of this sort would tend to affect the overall results, if e-voting counties different demographically from other counties (which is apparently the case in Florida). Another possibility is that e-voting affects voter behavior somehow, perhaps affecting different groups of voters differently. Maybe e-voting scares away some voters, or makes people wait longer to vote. Maybe the different user interface on e-voting systems makes straight party-line voting more likely or less likely.

This looks like the beginning of a long debate.