Automated Certificate Management Environment - Definition from the Hotspot Shield Glossary
The Automated Certificate Management Environment is a communication protocol that aims to automate interactions between users and certificate authorities. The protocol allows the automatic deployment of public key infrastructure for authentication and security at an extremely low cost compared to the previous costly and slow manual process.
Based on passing messages over HTTPS using JSON, the protocol has been standardized by the IETF. There are open source applications of ACME available for free downloading, and several web servers have added the protocol in as a standardized function.