I got a textbook that had a piece of lint embedded in a sticker. I don’t remember the actual authentication workflow, but I think the idea was to enter a code t

I got a textbook that had a piece of lint embedded in a sticker. I don’t remember the actual authentication workflow, but I think the idea was to enter a code to a website, which would pull up a series of photos and you could select the right one, like a captcha.