  Many augmented reality (AR) applications rely on omnidirectional environment
lighting to render photorealistic virtual objects. When the virtual objects
consist of reflective materials, such as a metallic sphere, the required
lighting information to render such objects can consist of privacy-sensitive
information that is outside the current camera view. In this paper, we show,
for the first time, that accuracy-driven multi-view environment lighting can
reveal out-of-camera scene information and compromise privacy. We present a
simple yet effective privacy attack that extracts sensitive scene information
such as human face and text information from the rendered objects, under a
number of application scenarios.
  To defend against such attacks, we develop a novel $IPC^{2}S$ defense and a
conditional $R^2$ defense. Our $IPC^{2}S$ defense, used in conjunction with a
generic lighting reconstruction method, preserves the scene geometry while
obfuscating the privacy-sensitive information. As a proof-of-concept, we
leverage existing OCR and face detection models to identify text and human
faces from past camera observations and blur the color pixels associated with
detected regions. We evaluate the visual quality impact of our defense by
comparing rendered virtual objects to ones rendered with a generic
multi-lighting reconstruction technique, ARKit, and $R^2$ defense. Our visual
and quantitative results demonstrate that our defense leads to structurally
similar reflections with up to 0.98 SSIM score across a variety of rendering
scenarios while preserving sensitive information by reducing the automatic
extraction success rate to at most 8.8%.
