PrivateEye: In-Sensor Privacy Preservation Through Optical Feature Separation

We address privacy issues in applications where images captured by an edge device (camera) are sent to the cloud for inference on utility tasks such as classification. Sending raw images to the cloud exposes them to data sniffing attacks and misuse by untrusted third-party service providers beyond the user's intended tasks. We propose an encoding scheme that not only evades direct visual inspection to the images or image reconstruction, but also prevents sensitive information from being ascertained. Unlike commonly used adversarial learning approaches, the proposed method is two-fold: first, it uses a diffractive optical neural network to spatially separate features corresponding to different tasks on the sensor plane in the optical domain. Then only the pixels corresponding to the utility task region are read. This encoding ensures that private features are never digitally stored on the edge device, thereby preventing privacy leakage. The proposed method successfully reduces the privacy retrieval in binary tasks with minimal accuracy loss (~ 2%) of the utility task, while reducing private task accuracy by ~ 35% and defending against reconstruction attacks with SSIM score of 0.43.