Let’s Encrypt: Every Server on the Internet Should Have a Certificate


The web is not secure. As of August 2016, only 45.5 percent of Firefox page loads are HTTPS, according to Josh Aas, co-founder and executive director of Internet Security Research Group. This number should be 100 percent, he said in his talk called “Let’s Encrypt: A Free, Automated, and Open Certificate Authority” at LinuxCon North America.

Why is HTTPS so important? Because without security, users are not in control of their data and unencrypted traffic can be modified. The web is wonderfully complex and, Aas said, it’s a fool’s errand to try to protect this certain thing or that. Instead, we need to protect everything. That’s why, in the summer of 2012, Aas and his friend and co-worker Eric Rescorla decided to address the problem and began working on what would become the Let’s Encrypt project.

The web is not secure because security is seen as too difficult, said Aas. But, security only involves two main requirements: encryption and authentication. You can’t really have one without the other. The encryption part is relatively easy; the authentication part, however, is hard and requires certification. As the two developers explored various options to address this, they realized that any viable solution meant they needed a new Certificate Authority (CA). And, they wanted this CA to be free, automated, open, and global.

These features break down some of the existing obstacles to authentication. For example, making authentication free makes it easy to obtain, automation brings ease of use, reliability, and scalability, and the global factor means anyone can get a certificate.

In explaining the history of the project, Aas said they spent the first couple of years just building the foundation of the project, getting sponsors, and so forth. Their initial backers were Akamai, Mozilla, Cisco, the EFF, and their CA partner was IDenTrust. In April of 2015, however, Let’s Encrypt became a Linux Foundation project, and The Linux Foundation’s organizational development support has allowed the project to focus on their technical operations, Aas said.

Built-in Is Best

Let’s Encrypt works through the ACME protocol, which is “DHCP for certificates,” Aas said. The Boulder software implements ACME, running on the Let’s Encrypt infrastructure, consisting of 42 rack units of hardware between two highly secure sites. Linux is the primary operating system, and there’s a lot of physical and logical redundancy built in.

They issue three types of certificates and have made the process of getting a certificate as simple as possible.

“We want every server on the Internet to have a certificate,” said Aas.

The issuance process involves a series of challenges between the ACME client and ACME server. If you complete all the challenges, you get a cert. The challenges, which are aimed at proving you have control over the domain, include putting a file on your web server, provisioning a virtual host at your domain’s IP address, or provisioning a DNS record for your domain. Additionally, there are three types of clients to use: simple, full-featured, and built-in — the last of which is preferred.

“Built-in is the best client experience,” Aas said. “It all just happens for you.”

Currently, Let’s Encrypt certificates have a 90-day lifetime. Shorter lifetimes are important for security, Aas said, because they encourage automation and limit damage in the case of compromise. This is still not ideal, he noted. Revocation is not an option, so if the certificate gets stolen, you’re stuck until it expires. For some people, 90 days is still too long, and shorter lifetimes are something they’re considering. Again, Aas said, “If it’s all automated, it doesn’t matter… It just happens.”

Additionally, Aas noted that Let’s Encrypt’s policy is not to revoke certificates based on suspicion. “Do you really want CAs to be the content police of the web?” Let’s Encrypt doesn’t want to be in that position; it becomes censorship, he said.

Let’s Encrypt now has 5.3 million active certs, which equates to 8.5 million active domains. And, Aas said, 92 percent of Let’s Encrypt certificates are issued to domains that didn’t have certificates before.

He concluded by saying that we have a chance within 2016 to create a web that is more encrypted than not. You can take the next step by adopting encryption via TLS by default.