Several years ago, I wrote "Is it SSL, TLS or HTTPS?" This was a simple blog to talk about the difference between the terms and which term I would use.
A lot has happened in the years since I wrote that blog post. The secure protocol called SSL has been deprecated, and everyone is now using TLS. But we all still say SSL. Let's discuss.

Secure Sockets Layer (SSL)

To sum up the discussion in my earlier blog, SSL was originally developed by Netscape and was followed up with SSL 2.0 in 1995. SSL 3.0 was released in 1996. SSL 3.0 was quite similar to TLS 1.0, but the differences were significant enough that they did not interoperate. As such, operating systems and browsers supported both SSL 3.0 and TLS 1.0.

Unfortunately, old standards just don't go away until someone or an incident provokes their deprecation. The POODLE attack of 2014 and the DROWN attack of 2016 put an end to browser support of SSL 2.0 and 3.0.

Transport Layer Security (TLS)

TLS was introduced by the IETF in January 1999. I'm not sure why they changed the naming from Secure Sockets Layer to Transport Layer Security. Perhaps SSL was really a Netscape handle, and the IETF didn't want to create any confusion. Nevertheless, the acronym changed from SSL to TLS.
TLS 1.0 was initially very popular when it was rolled out alongside SSL 3.0. However, when it was discovered that TLS 1.0 and 1.1 could be vulnerable to a POODLE attack if the implementations of these protocols were not configured properly, their popularity quickly fell, and TLS 1.2 was the only protocol to be considered secure.

In 2016, PCI issued a paper – "Migrating from SSL and Early TLS". In this paper, they required merchants to deprecate SSL and early TLS (i.e., TLS 1.0 and 1.1) and migrate to TLS 1.2 by June 30, 2018. Many other secure servers also migrated to TLS 1.2 in 2018. Entrust Datacard stopped supporting TLS 1.0 and 1.1 in 2018.

In addition, browser and operating system vendors plan to deprecate TLS 1.0 and 1.1 starting in 2020. Will this leave us with only TLS 1.2?

Fortunately, RFC 8446 for TLS 1.3 was published in August 2018. Researchers have learned from past mistakes to develop in TLS 1.3 a much more secure version than its predecessor, TLS 1.2. Many attributes used in vulnerabilities are just not supported in TLS 1.3. Downgrade protection has also been added to prevent an attacker from forcing the secure session to drop to a lower version of the protocol. We expect rapid deployment of TLS 1.3 in 2019.

SSL vs. TLS

Netcraft provides the following data illustrating server support of SSL and TLS based on data accumulated after surveying over 61 million servers.

Protocol Version Percentage (April 2019)
SSL 3.0 0
TLS 1.0 0.91
TLS 1.1 0.01
TLS 1.2 77.71
TLS 1.3 21.37

Although SSL 3.0 says 0%, there were actually 92 servers observed still running this version. As such, the SSL version of the protocol is dead, and TLS 1.0/1.1 aren't far behind.

So, what name should we use?

A quick Google search on SSL certificate versus TLS certificate returned 226,000,000 and 29,500,000 responses respectively. SSL is quite simply the most popular term for discussing and marketing secure server certificates. Most of the time, I will combine the terms and call them SSL/TLS certificates.

Bruce Morton

Bruce Morton has worked in the public key infrastructure and digital certificate industry for more than 15 years and has focused on SSL and other publicly trusted certificates since 2005. He has been an active member of the CA/Browser Forum that released guidelines for extended validation (EV) certificates and Baseline Requirements for SSL certificates. Bruce oversees the governance and compliance of Entrust’s publicly trusted PKI.