[dward]

Google has been experimenting with and deploying blockchain technology since before 2013. Certificate Transparency[0], designed at Google, stores certificates in a distributed merkle tree. Any certificate that Chrome accepts as valid is stored in the certificate transparency merkle tree.

[0]https://tools.ietf.org/html/rfc6962

[Shoothe]

Well it may be splitting hair but there is no proof or work and the number of nodes is certainly smaller.

There is also CONIKS and Google's Key Transparency.

This comes to my mind: https://medium.com/@bbc4468/centralized-vs-decentralized-vs-...