Keytree is a next-generation open public-key infrastructure.
Keytree is federated and has no central servers. Anyone can run a Keytree server. I ran a server on https://keytree.io, and you can run your own server by downloading the code using "go get github.com/jellevandenhooff/keytree/keytree-server" and running "keytree-server".
To register an e-mail address with Keytree, download and run "keytree-client".
This repository is under development. The code has not been audited and most definitely contains bugs.