Differential Privacy Configurations in the Real World: A Comparative Analysis

An increasing number of technologies depend on the large-scale collection of individual-level data, whether for gathering statistical insights from billions of users or training AI models. However, reliance on personal data raises privacy concerns that, in turn, limit the collection and analysis essential to these technologies. Differential Privacy (DP) has gained traction in both academia and industry, ensuring privacy by adding carefully crafted noise to data or its outputs based on a pre-defined DP parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>. As real-world implementations emerge, we can examine how DP is practically used beyond academic settings, supporting industry adoption and expanding knowledge on DP applications. Using a systematic process, we comprehensively surveyed the deployed parameters of DP configurations in both commercial and governmental implementations (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n=140$</tex-math></inline-formula>) and compared them to those employed in academic research. We also propose a high-level taxonomy for DP configuration, capturing practical implementations of differentially private Machine Learning (ML) and Federated Learning (FL) applications, highlighting key factors, including the privacy unit and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>. Our results show that, on average, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> values utilized in the industry span a wider range than those in academic research, with distinct configuration policies for governmental and commercial organizations. Moreover, we identified contrasting reasoning behind <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> selection across deployment environments, alongside insufficient transparency in industry disclosures of DP parameters and limited support for user-oriented configuration. Finally, we discuss how the collected knowledge can be used to create methodological guidelines for the configuration of DP in real-world environments, supporting the vision of an Epsilon Registry.