Differentially Private Synthetic Data via APIs 3: Using Simulators Instead of Foundation Model

Differentially private (DP) synthetic data enables the use of sensitive datasets while providing strong privacy guarantees. Recently, Private Evolution (PE) has emerged as a promising framework for generating DP synthetic data using only inference APIs of foundation models. However, suitable foundation models are not always available for every private data domain. In this paper, we show that PE is more general than previously understood and can incorporate APIs beyond foundation models. In particular, we show that state-of-the-art non-neural-network data synthesizers, including computer graphics-based image generators and physics simulation tools (which we refer to as simulators), integrate naturally into PE. We call the resulting method Sim-PE. Sim-PE broadens the applicability of PE while improving performance. For image synthesis, Sim-PE improves downstream classification accuracy by up to 3x, reduces FID by up to 80%, and is significantly more efficient. We further show that simulators and foundation models can be seamlessly combined within Sim-PE for additional gains. Beyond performance improvements, Sim-PE enables new DP applications that are difficult or impossible for existing methods, including generating DP control signals whose execution reproduces the distribution of private observations. The code is open-sourced in the Private Evolution Python library: https://github.com/microsoft/DPSDA