A Beginner’s Guide to TLS/SSL Certificates and Website Security

Raise your hand if the company that you work for has a website, or you, yourself, run a website. That’s a lot of hands!

What Is TLS/SSL?

We often talk as if Transport Layer Security (TLS) and Secure Sockets Layer (SSL) are the same thing, however, their more like successor and predecessor. Both are cryptographic protocols that are designed for secure communications. The last version of the SSL protocol was 3.0 and was published by the IETF in 1996. A major vulnerability, given the name POODLE, was disclosed in 2014, which essentially brought an end to SSL.

TLS 1.0 was defined as an upgrade to SSL in a request for comments (RFC) in 1999. The protocols aren’t substantially different, and the name change had more to do with the fact that the IETF wanted to ensure that it was apparent that this was a fork of the protocol.

Regardless of whether we say SSL Certificates or TLS Certificates, we’re almost certainly using the TLS protocol.

Website TLS/SSL Certificates

A TLS/SSL Certificate is a pair of files where one file contains a private key that only the server knows, and a public key that is used to create a trusted relationship. A process known as a “handshake” occurs when you visit a website that uses an SSL certificate. This handshake can be a little confusing, but the below diagram does a pretty good job.

Source: https://www.entrust.com/resources/certificate-solutions/learn/how-does-ssl-work

How TLS/SSL Protects Your Website

The purpose of a TLS/SSL Certificate is to create a trusted relationship between your computer’s web browser, and the server hosting the website. Once this relationship is created, any communication between these two points, your browser and the website server, is encrypted using the private key that only the server has knowledge of. This is how TLS/SSL protects a website visitor’s financial information, such as credit card number, when they enter it into a form on your website.

Along with Encryption, the TLS/SSL protocol are ensuring a form of Authentication and Integrity. Once the relationship is established you can be sure that the communications being exchanged aren’t being manipulated and are being sent and received by the same two parties.

TLS/SSL Testing

Not all TLS/SSL Certificates are the same, and not all website servers implement these certificates in the same way. Implementing TLS/SSL incorrectly, or not configuring the web server with the appropriate settings, can lead to insecurities. Testing your TLS/SSL should be added to your annual checklist and can ensure that your TLS/SSL Certificates are in tip-top shape.

Here are some resources that you can use to easily test your websites.

  • SSL Labs by Qualys – One of our favourites; allows you to hide the results from their community boards for added privacy.
  • Mozilla Observatory – Choose to not show up in public results, and even not get scanned by third-party scanners. Observatory not only scans for TLS/SSL issues, but also for HTTP and SSH issues.
  • Wormly – Wormly gives you a simple TLS/SSL health check report.
  • CryptCheck – Something a little more technical; CryptCheck also runs tests on SSH, SMTP and XMPP.
  • SSL Checker – Visualize and verify the certificate chain.
  • TLS Version Check by Geekflare – Quickly check if your web server uses a deprecated version of TLS.
  • How’s My SSL? – They really mean, “TLS”. How’s My SSL gives you a simple report and rating on your TLS certificate. It also offers an API.
  • Digicert SSL Installation Diagnostics Tools – Diagnostics tool that also allows you to check for common vulnerabilities.
  • SSL Checker – SSL Shopper providers another tools for verifying your TLS/SSL certificate install.

Other Resources

The Mozilla wiki has a great resource that includes details on TLS cipher suites and other TLS configurations to help you improve web server security. I’d be remiss if I didn’t mention the Mozilla Developer Network (MDN) Web Docs which is rife with articles, references, and guides for better web development.

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