Let's Encrypt ACME Certificate Protocol Set for Standardization

Automated Certificate Management Environment (ACME) is set to become an internet standard later this year.

SSL/TLS certificates

The open-source Let's Encrypt project has been an innovating force on the security landscape over the last several years, providing millions of free SSL/TLS certificates to help secure web traffic. Aside from the disruptive model of providing certificates for free, Let's Encrypt has also helped to pioneer new technology to help manage and deliver certificates as well, including the Automated Certificate Management Environment (ACME).

ACME is no longer just a Let's Encrypt effort at this point in 2017 and is now being standardized by the Internet Engineering Task Force (IETF). The ACME protocol can be used by a Certificate Authority (CA) to automate the process of verification and certificate issuance.  

"The protocol also provides facilities for other certificate management functions, such as certificate revocation," the IETF draft of the ACME standard states.

The ACME protocol being standardized at the IETF is version 2 of the protocol and benefits from the wider participation of other internet organizations' viewpoint on certificate management, beyond just Let's Encrypt. Though the IETF standardization process is a multi-stakeholder effort, Josh Aas, Executive Director and Co-Founder of Internet Security Research Group (ISRG) and Let's Encrypt, noted that the process has gone as expected with no real surprises. 

"We expect the standardization process to conclude in the next few months," Aas told eWEEK.

Let's Encrypt is a non-profit effort that was announced in November 2014 and became a Linux Foundation Collaborative Project in April 2015. Let's Encrypt exited its beta period in April 2016 and currently is helping to secure over 43 million websites.

Aas said that the ACME v1 protocol is what Let's Encrypt uses today, and version 2 will be standardized by the IETF and supported by Let's Encrypt as of January 2018. The main difference between the two versions is the order of operations.

"In v1, clients authorize a set of domains and then request a certificate," Aas said. "In v2 clients request a certificate and then authorize domains for the certificate. The latter ordering offers more flexibility to us and other CAs who might be interested in using ACME. "

As a Certificate Authority (CA), to date Let's Encrypt has only provided Domain Validated (DV) certificates. DV certificates do not specifically identify or validate the organization using the certificate, but rather validate a request against a domain registry. In contrast, an Organization Validated (OV) certificate identifies the organization and validates the identity against a business registry. An Extended Validation (EV) provides the highest level of validation for an organization and involves a comprehensive vetting process. 

"ACME v1 was designed primarily with DV issuance in mind," Aas said. "ACME v2 can probably not be used to issued OV or EV certificates on its own, but it can play a role in issuing OV or EV certificates."

Aas added that ACME V2 could potentially be used in OV and EV certificate issuance by automating the parts of validation process that can be automated.

While Let's Encrypt will be making use of the IETF ACME v2 protocol, other Certificate Authorities are taking a cautious approach.

"Symantec offers an automation agent, SSL Assistant Plus, which implements a proprietary certificate lifecycle protocol," Rick Andrews, Symantec Distinguished Engineer told eWEEK. "We follow the ACME development discussions in the IETF, and are considering adding support for the ACME protocol."

Sean Michael Kerner

Sean Michael Kerner

Sean Michael Kerner is an Internet consultant, strategist, and contributor to several leading IT business web sites.