Apple’s “white paper” on Face ID appears to have been removed
Many articles such as [https://9to5mac.com/2017/09/27/face-id-iphone-x-white-paper/](https://9to5mac.com/2017/09/27/face-id-iphone-x-white-paper/) have referenced the URL of a white paper on Face ID [https://images.apple.com/business/docs/FaceID_Security_Guide.pdf](https://images.apple.com/business/docs/FaceID_Security_Guide.pdf) which appears to have been removed as it now just redirects you to the support page. None of the original articles with this link contain any updates.
Interested in learning more about the technology from the company’s perspective, preferably from an engineering standpoint, but most preferably *without* having to dig through secondhand sources bereft of technical specifications like editorialized news articles or user-oriented support pages.
Is anyone aware of a new URL at which the same paper can be found? Or a similar primary source? Would appreciate it