An exercise in careful misreading

A recent article was passed along to me:

Jane Bambauer, Krishnamurty Muralidhar, and Rathindra Sarathy
Fool’s Gold: An Illustrated Critique of Differential Privacy
Vanderbilt Journal of Entertainment and Technology Law 16(4):701-755.

The article is aimed at the legal community, which has seen in differential privacy a potential technological solution for data privacy issues. The goal of the article is to throw some cold water on some law scholars’ embrace of differential privacy as a solution concept. I’m not a one-method-fixes-all kind of person, but this article is sort of relentlessly negative about differential privacy based solely on a single mechanism: output perturbation. The authors appear to be laboring under the impression that this is really the only way to provide differential privacy, “an assumption that contorts the rest of [their] analysis,” the charge that they level at one proponent of differential privacy.

In the example with which they open the paper, they claim that “even knowing the distribution of noise that is randomly added to each cell, the internist has no hope of interpreting the response. The true values could be almost anything.” While technically true, it’s quite misleading. Indeed, by knowing the distribution, one can create bounds on the accuracy of the answer — this is, contra the authors’ claims, the “tension between utility and privacy” that differential privacy researchers do “toil” with. They manage to explain the statistics fairly reasonably in the middle of the paper but ignore that in the introduction and conclusion in favor of some ascerbic bons mots. Now, perhaps to them, privacy should be an almost-sure guarantee. There is a critique in that: differential privacy can only make probabilistic guarantees, and if your legal standard is stricter than that, then it’s probably not a good way to go. But the misleading rhetoric employed here is meant to stir emotions rather than sway the intellect.

The language in the article is quite florid: “Differential privacy has been rocking the computer science world for over ten years and is fast becoming a crossover hit among privacy scholars and policymakers.” I suppose this sort of prose may be what constitutes scholarly writing in law, but it lacks the measured tones that one might want in more objective criticism. Perhaps they read academic writing in science and engineering in an equally emotional register. They use some strong language to conclude “differential privacy is either not practicable or not novel.” I find such blanket statements both puzzling and vacuous. If you set up a straw-man of what differential privacy is, I suppose you can derive such dichotomies, but is that the best argument one can make?

One thing that comes out of this reading is that most people don’t really appreciate how technology progresses from academic research to practical solutions. Perhaps some legal scholars have overstated the case for differential privacy based on the state of the technology now. But whose to say how things will look a few years down the line? We’ll have better algorithms, different database structures, and different data sharing mechanisms and platforms. Perhaps differential privacy is not ready for prime time, although Google seems to disagree. The authors’ main point (hidden in the in the breathless indignation) is that it’s probably not the best solution for every data sharing problem, a statement with which I can completely agree.

In their effort to discredit differential privacy, the authors ignore both the way in which scientific and academic research works as well as contemporary work that seeks to address the very problems they raise: context-awareness via propose-test-release, methods for setting \epsilon in practical scenarios, and dealing with multiple disclosures via stronger composition rules. They further ignore real technical hurdles in realizing “pure” differential privacy in favor of “illustrations” with the goal of painting proponents of differential privacy as ideologues and hucksters. Of course context and judgement are important in designing query mechanisms and privacy-preserving analysis systems. Furthermore, in many cases microdata have to be released for legal reasons. I think few people believe that differential privacy is a panacea, but it at least provides a real quantifiable approach to thinking about these privacy problems that one can build theories and algorithms around. The key is to figure out how to make those work on real data, and there’s a lot more research to be done on that front.

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Readings

Tiassa, by Steven Brust. As Cosma puts it, mind candy, and only worth reading if you’ve read the other 10 books in the series. Quite enjoyable, however.

Kraken, by China Miéville. A rollicking adventure involving a giant squid, horrific monsters and gruesome deaths, a dark underbelly of London, the end of the world, and… a ghost piggie. Among other things. I enjoyed it.

Hindoo Holiday, by J.R. Ackerley. A travelogue of a gay Englishman who becomes an attaché to a gay Raja in a princely state in the early 20th century. Often full of colonial condescension (though in a light tone) about things Indian. Most of us are tragically sad of buffoonish. The homosexuality is not overt but explicit enough that the book was censored when published. Still, it’s an interesting historical read, just because it is so weird.

The Lost Promise of Civil Rights, by Risa Goluboff. A really fascinating book about the history of civil rights litigation in the US from Lochner to Brown. The term “civil rights” was in a state of flux during that era, transitioning from a labor-based understanding to discrimination-based standing. The main players were the Justice Department’s Civil Rights Service and the NAACP. By choosing which cases to pursue and which arguments to advance, they explored different visions of what civil rights could mean and why they were rights in the first place. In particular, the NAACP did not take on many labor cases because they were actively pursuing a litigation agenda that culminated in Brown. The decision in Brown and subsequent decisions shaped our modern understanding of civil rights as grounded in stopping state-sanctioned discrimination. However, the “lost promise” in the title shows what was lost in this strategy — the state-sponsored parts of Jim Crow were taken down, but the social institutions that entrench inequality were left.

The Devil in the White City, by Erik Larson. I had to read this since I just moved to Chicago and I work right near Jackson Park. This was a very engaging read (Larson just has that “style”) but a bit creepy in that “watched too many episodes of Dexter” way. I enjoyed it a little less than Thunderstruck, but I had more professional attachment to that one.

Quote of the day

From a recent read, Risa Goluboff’s The Lost Promise of Civil Rights:

The process of doctrinal distillation was particularly powerful in the years leading up to Brown. The multiplicity of the civil rights practices of the 1940s reflected both the unsettled nature of legal doctrine and the complexity of challenging a seventy-five-year-old racial and economic caste system. As lawyers transformed into legal claims attacks on the unwieldy thing called Jim Crow, they chose particular cases, particular legal theories, and particular formulations of injury that they thought legal doctrine could remedy. As a result, the civil rights case that took the definitive step towards undermining Jim Crow would, as Brown did, both embody a legal understanding of what Jim Crow was and begin to define the constitutional response to it. In so doing, that case would, as Brown also did, elide the forms of civil rights and understandings of Jim Crow that lawyers had chosen to filter out of the litigation process.

This book is a fascinating read (more so if you are a lawyer, I imagine) about how it is that we think of civil rights in the way that we do now, and how a lot of the multiple meanings of civil rights (in particular labor rights) were articulated in the years before Brown vs. Board of Education. Civil rights claims were launched on behalf of black workers by the Civil Rights Section of the DoJ as well as the NAACP, and the latter chose a very particular approach to Brown which did not build on a lot of the victories won in those earlier cases.