Security and Privacy Research at the University of Virginia

Our research seeks to empower individuals and organizations to control how their data is used. We use techniques from cryptography, programming languages, machine learning, operating systems, and other areas to both understand and improve the privacy and security of computing as practiced today, and as envisioned in the future. A major current focus is on adversarial machine learning.

Everyone is welcome at our research group meetings. To get announcements, join our Slack Group (any @virginia.edu email address can join themsleves, or email me to request an invitation).

Recent Posts

ICLR DPML 2021: Inference Risks for Machine Learning

I gave an invited talk at the Distributed and Private Machine Learning (DPML) workshop at ICLR 2021 on Inference Risks for Machine Learning.

The talk mostly covers work by Bargav Jayaraman on evaluating privacy in machine learning and connecting attribute inference and imputation, and recent work by Anshuman Suri on property inference.


How to Hide a Backdoor

The Register has an article on our recent work on Stealthy Backdoors as Compression Artifacts: Thomas Claburn, How to hide a backdoor in AI software — Neural networks can be aimed to misbehave when squeezed, The Register, 5 May 2021.


Codaspy 2021 Keynote: When Models Learn Too Much

Here are the slides for my talk at the 11th ACM Conference on Data and Application Security and Privacy:

When Models Learn Too Much [PDF]

The talk includes Bargav Jayaraman’s work (with Katherine Knipmeyer, Lingxiao Wang, and Quanquan Gu) on evaluating privacy in machine learning, as well as more recent work by Anshuman Suri on property inference attacks, and Bargav on attribute inference and imputation:


CrySP Talk: When Models Learn Too Much

I gave a talk on When Models Learn Too Much at the University of Waterloo (virtually) in the CrySP Speaker Series on Privacy (29 March 2021):

Abstract

Statistical machine learning uses training data to produce models that capture patterns in that data. When models are trained on private data, such as medical records or personal emails, there is a risk that those models not only learn the hoped-for patterns, but will also learn and expose sensitive information about their training data. Several different types of inference attacks on machine learning models have been found, and methods have been proposed to mitigate the risks of exposing sensitive aspects of training data. Differential privacy provides formal guarantees bounding certain types of inference risk, but, at least with state-of-the-art methods, providing substantive differential privacy guarantees requires adding so much noise to the training process for complex models that the resulting models are useless. Experimental evidence, however, suggests that inference attacks have limited power, and in many cases a very small amount of privacy noise seems to be enough to defuse inference attacks. In this talk, I will give an overview of a variety of different inference risks for machine learning models, talk about strategies for evaluating model inference risks, and report on some experiments by our research group to better understand the power of inference attacks in more realistic settings, and explore some broader the connections between privacy, fairness, and adversarial robustness.


Improved Estimation of Concentration (ICLR 2021)

Our paper on Improved Estimation of Concentration Under ℓp-Norm Distance Metrics Using Half Spaces (Jack Prescott, Xiao Zhang, and David Evans) will be presented at ICLR 2021.

Abstract: Concentration of measure has been argued to be the fundamental cause of adversarial vulnerability. Mahloujifar et al. (2019) presented an empirical way to measure the concentration of a data distribution using samples, and employed it to find lower bounds on intrinsic robustness for several benchmark datasets. However, it remains unclear whether these lower bounds are tight enough to provide a useful approximation for the intrinsic robustness of a dataset. To gain a deeper understanding of the concentration of measure phenomenon, we first extend the Gaussian Isoperimetric Inequality to non-spherical Gaussian measures and arbitrary ℓp-norms (p ≥ 2). We leverage these theoretical insights to design a method that uses half-spaces to estimate the concentration of any empirical dataset under ℓp-norm distance metrics. Our proposed algorithm is more efficient than Mahloujifar et al. (2019)‘s, and experiments on synthetic datasets and image benchmarks demonstrate that it is able to find much tighter intrinsic robustness bounds. These tighter estimates provide further evidence that rules out intrinsic dataset concentration as a possible explanation for the adversarial vulnerability of state-of-the-art classifiers.

Here’s Jack’s video summary of the work:

Paper: arXiv, Open Review
Code: https://github.com/jackbprescott/EMC_HalfSpaces