Proof of Capture: Apple Reference Image, but open source and using steganography

The authors created a camera that embeds a signed perceptual hash into image pixels using a DWT-DCT watermark that survives compression and resizing, with signatures generated by an ATECC608 chip whose private key remains on-device. An open-source proof-of-capture implementation costs under $100 and shows the signed watermarks survive cropping and WhatsApp-grade recompression.