Guided Diffusion Model for Sensor Data Obfuscation

Sensor data collected by Internet of Things (IoT) devices carries detailed information about individuals in their vicinity. Sharing this data with a semi-trusted service provider may compromise the individuals' privacy, as sensitive information can be extracted by powerful machine learning models. Data obfuscation empowered by generative models is a promising approach to generate synthetic sensor data such that the useful information contained in the original data is preserved and the sensitive information is obscured. This newly generated data will then be shared with the service provider instead of the original sensor data. In this work, we propose PrivDiffuser, a novel data obfuscation technique based on a denoising diffusion model that attains a superior trade-off between data utility and privacy through effective guidance techniques. Specifically, we extract latent representations that contain information about public and private attributes from sensor data to guide the diffusion model, and impose mutual information-based regularization when learning the latent representations to alleviate the entanglement of public and private attributes, thereby increasing the effectiveness of guidance. Evaluation on three real-world datasets containing different sensing modalities reveals that PrivDiffuser yields a better privacy-utility trade-off than the state-of-the-art obfuscation model, decreasing the utility loss by up to $1.81\%$ and the privacy loss by up to $3.42\%$. Moreover, we showed that users with diverse privacy needs can use PrivDiffuser to protect their privacy without having to retrain the model.