[davidperrenoud]

Certificate Transparency. Both Chrome and Safari implement it and you will receive an e-mail from Cloudflare if someone creates a certificate for your domain:

It is kind of a blockchain with proof of authority. More precisely it is a Merkle tree with certificate authorities seen as trusted nodes by the web browsers. This idea was extended in something called General Transparency and implemented in the Google Trillian project: https://sites.google.com/site/certificatetransparency/genera...

[kaoD]

When people refer to "crypto" they mean cryptocurrency. In a more general non-currency sense they still refer to trustless blockchains that solve the Byzantine Generals Problem.