Rising Stars 2020:

Amrita Roy Chowdhury

PhD Candidate

University of Wisconsin-Madison

Areas of Interest

  • Security
  • Privacy


Crypt𝜖: Crypto-Assisted Differential Privacy on Untrusted Servers


Differential privacy (DP) is currently the de-facto standard for achieving privacy in data analysis, which is typically implemented either in the ''central'' or ''local'' model. The local model has been more popular for commercial deployments as it does not require a trusted data collector. This increased privacy, however, comes at the cost of utility and algorithmic expressibility as compared to the central model.

In this work, we propose, Crypt𝜖, a system and programming framework that (1) achieves the accuracy guarantees and algorithmic expressibility of the central model (2) without any trusted data collector like in the local model. Crypt𝜖 achieves the ''best of both worlds'' by employing two non-colluding untrusted servers that run DP programs on encrypted data from the data owners. In theory, straightforward implementations of DP programs using off-the-shelf secure multi-party computation tools can achieve the above goal. However, in practice, they are beset with many challenges like poor performance and tricky security proofs. To this end, Crypt𝜖 allows data analysts to author logical DP programs that are automatically translated to secure protocols that work on encrypted data. These protocols ensure that the untrusted servers learn nothing more than the noisy outputs, thereby guaranteeing DP for all Crypt𝜖 programs. Crypt𝜖 supports a rich class of DP programs that can be expressed via a small set of transformation and measurement operators followed by arbitrary post-processing. Further, we propose performance optimizations leveraging the fact that the output is noisy. As a result, Crypt𝜖 achieves performance that is practical for real-world usage.


Amrita Roy Chowdhury is a PhD candidate in the Computer Sciences department at the University of Wisconsin-Madison, advised by Prof. Somesh Jha. She completed her Bachelor of Engineering in Computer Science from the Indian Institute of Engineering Science and Technology, Shibpur where she was awarded the President of India Gold Medal for being the top graduating student across all departments. Her research explores the synergy between differential privacy and cryptography through novel algorithms that expose the rich interconnections between the two areas, both in theory and practice.

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