https://www.vice.com/en_us/article/bvznd4/cryptographic-attestation-of-personhood-c

Everyone hates CAPTCHA’s. Those little puzzles we all have to navigate to prove to websites that we’re humans and not robots consume an incredible amount of our time and often feel like they don't work. Typing words was bad enough, selecting all the street signs or boats in blurry pictures is worse. Cloudflare research engineer Thibault Meunier estimates humanity collectively wastes roughly 500 years every day solving captchas. So the company has devised a system that could end them forever.

“It takes a user on average 32 seconds to complete a CAPTCHA challenge. There are 4.6 billion global Internet users. We assume a typical Internet user sees approximately one CAPTCHA every 10 days,” Meunier said. “This very simple back of the envelope math equates to somewhere in the order of 500 human years wasted every single day—just for us to prove our humanity.”