Automated Certificate Management Environment

https://datatracker.ietf.org/wg/acme/charter/
https://github.com/ietf-wg-acme/acme

https://letsencrypt.org/ - Let's Encrypt - Free SSL/TLS Certificates

acme4j

Java client for ACME (Let's Encrypt)

https://github.com/shred/acme4j
https://acme4j.shredzone.org/

This is a Java client for the Automatic Certificate Management Environment (ACME) protocol as specified in RFC 8555.

https://github.com/certbot/certbot - Certbot, previously the Let's Encrypt Client, is EFF's tool to obtain certs from Let's Encrypt, and (optionally) autoenable HTTPS on your server
https://github.com/Neilpang/acme.sh - An ACME Shell script, a certbot client: acme.sh https://acme.sh
https://github.com/diafygi/acme-tiny - A tiny script to issue and renew TLS certs from Let's Encrypt
https://github.com/porunov/acme_client - Java ACME Client application
https://github.com/letsencrypt/boulder - An ACME-based CA, written in Go
https://gitlab.com/ID4me/Acme - ACME Server Java implementation based on https://tools.ietf.org/html/draft-ietf-acme-acme-09