In the .com days, I was active in the e-commerce space, using public-key cryptography to solve problems. We had digital certificates, digital signatures, etc, w

In the .com days, I was active in the e-commerce space, using public-key cryptography to solve problems. We had digital certificates, digital signatures, etc, which we used to solve various problems like authenticating and securing access to websites, creating encrypted and signed emails, etc. One thing was non-repudiation, i.e. if I send you a digitally-signed email with a purchase order, then you can legally rely on it. There were some attempts to use similar techniques to allow trusted third parties to register documents, but nobody was willing to pay for the service.