Data Privacy and Cryptography Experts File Brief in Support of Census Bureau

BERKELEY, Calif., May 3, 2021 /PRNewswire/ -- Twenty leading experts, in data privacy and cryptography along with lawyers from Bondurant Mixson & Elmore filed an amicus brief in support of the Census Bureau's use of "differential privacy"—a mathematically rigorous way of providing provably and future-proof privacy-infused statistics— to protect the privacy of census respondents.

Through the lawsuit, the state of Alabama seeks to force the Census Bureau to use out-dated methods for protecting confidentiality—methods which a team of Census Bureau researchers found could be easily broken by deploying modern data reconstruction techniques to published Census statistics. The experts, who include inventors of differential privacy, cryptographers, statisticians, legal experts focused on technology and society document the increased risks of attacks due to the availability of large data sets and computing power available to adversaries, and explain that differential privacy is the only known method capable of preventing such attacks while simultaneously enabling the publication of useful statistics.

Cynthia Dwork, Gordon McKay Professor of Computer Science, Harvard University said: "The Census Bureau—like other statistical agencies—must adopt protections to fit changing threats. Thanks to fifteen years of research on differential privacy, the Census Bureau has the tools to meet its obligations to both provide useful statistical data and provide future-proof protection of privacy."

"To deliver robust privacy protections requires differential privacy implementation choices that reflect the real risks," said Deirdre Mulligan, Professor and Co-Director, Algorithmic Fairness & Opacity Group at the School of Information, University of California, Berkeley. "Privacy isn't free, and protecting it will, as it always has, reduce the accuracy of fine grained statistics, however that reduction is the price we pay for ongoing robust public participation in the census." 

According to Dwork: "The 'privacy vs accuracy' argument does not hold: Poor privacy now guarantees poor participation in the future."

Adam Smith, Professor of Computer Science and Electrical and Computer Engineering, Boston University stated: "Differential Privacy is the only proven methodology that secures data now and into the future."

The risk of re-identifying census respondents from the release of basic statistical tables, like those the Census Bureau releases, is real and growing and can impact tens of millions of Americans. The Census Bureau's research—as well as extensive academic research—shows that data reconstruction and re-identification attacks in which an attacker first reconstructs person-level data records from products based on aggregated personal data, and then, re-identifies the reconstructed records are increasingly easy. Data releases protected by traditional statistical disclosure limitation techniques, like those the state of Alabama wants the Census Bureau to use, are vulnerable to these attacks.  

A consensus study report published by the National Academies of Sciences, Engineering, and Medicine in 2017 concluded that traditional statistical disclosure methods "are increasingly susceptible to privacy breaches given the proliferation of external data sources and the availability of high-powered computing that could enable inferences about people or entities in a dataset, re-identification of specific people or entities, and even reconstruction of the original data."¹

"The data privacy experts filing today's brief should be lauded for sharing their insights on differential privacy with the Court and the public," said Michael B. Jones of Bondurant Mixson & Elmore LLP, the attorney for the experts. "The Census Bureau's disclosure avoidance system is essential to protecting the privacy of the millions of people who responded to the 2020 Census."

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¹ National Academies of Sciences, Engineering, and Medicine, Federal Statistics, Multiple Data
Sources, and Privacy Protection: Next Steps 104-05 (2017).

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SOURCE Bondurant Mixson & Elmore LLP