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Differentially Private Model Personalization
Prateek Jain · J K Rush · Adam Smith · Shuang Song · Abhradeep Guha Thakurta

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in Theory and Practice of Differential Privacy »
We study personalization of supervised learning with user-level differential privacy. Consider a setting with many users, each of whom has a training data set drawn from their own distribution $P_i$. Assuming some shared structure among the problems $P_i$, can users collectively learn the shared structure---and solve their tasks better than they could individually---while preserving the privacy of their data? We formulate this question using joint, _user-level_ differential privacy---that is, we control what is leaked about each user's entire data set. We provide algorithms that exploit popular non-private approaches in this domain like the Almost-No-Inner-Loop (ANIL) method, and give strong user-level privacy guarantees for our general approach. When the problems $P_i$ are linear regression problems with each user's regression vector lying in a common, unknown low-dimensional subspace, we show that our efficient algorithms satisfy nearly optimal estimation error guarantees. We also establish a general, information-theoretic upper bound via an exponential mechanism-based algorithm.

Author Information

Prateek Jain (Google Research)
J K Rush (Google)
Adam Smith (Boston University)
Shuang Song (Google)
Abhradeep Guha Thakurta (Google)

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