Understanding Wildcard SSL & How Does a Wildcard Certificate Work?

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Most prominent players in the digital certificate industry offer a variety of SSL/TLS certificates. As such, it’s natural for a customer to be confused about which SSL/TLS certificate to use on their website. If you have a host of subdomains where you want to use HTTPS, a wildcard SSL certificate might be a good fit, especially in terms of cost and ease of implementation.

What Is a Wildcard SSL Certificate?

A wildcard SSL certificate encrypts a website and an unlimited number of subdomains at a specific level using a single certificate. Besides being more cost-effective, it’s also easier to manage multiple subdomains on a single certificate than it is to fill out numerous certificate signing requests (CSRs) and manage multiple SSL/TLS certificates for individual URLs. A wildcard offers convenience in terms of hassle-free certificate management.

But how do wildcard certificates work? Let’s take a look:

How Do Wildcard SSL Certificates Work?

A standard SSL certificate will only protect a single domain. For example, if you have an SSL certificate for www.domain.com, then it won’t cover blog.domain.com. A wildcard certificate, on the other hand, is a public key certificate that secures both – your primary domain, as well as an unlimited number of subdomains at one level.

Let us consider the following example:

Bob owns a website that he feels is possibly overloaded with information in an unsystematic manner. He is afraid that new customers might find it hard to navigate, so he wants to segregate and organize it structurally using the following subdomains:

  • login.domain.com
  • products.domain.com
  • blog.domain.com

These first-level subdomains can all be secured under the same wildcard – *.domain.com.

Now, let’s take a look at some of his second-level subdomains: 

  • member.login.domain.com
  • dev.login.domain.com
  • mail.login.domain.com

These can be secured using *.login.domain.com. However, since Bob can only secure one level of subdomains per wildcard, this means that he would need to use an additional wildcard certificate to encrypt these second-level subdomains.

While a wildcard SSL certificate is a quick and economical solution for implementing HTTPS across all subdomains at a single level, there are some security concerns that you need to bear in mind. With wildcard SSL certificates, a private key is shared amongst all subdomains across all servers. If your domain is infiltrated by attackers, or if the certificate’s private key is compromised, illegitimate subdomains can be set up and utilized to run phishing campaigns. This sort of breach is not only hard to detect, but it also impacts the reputation of your brand.

For this reason, wildcard SSL certificates are available only for two validation levels: domain validation (DV) and organization validation (OV). Extended Validation (EV) is not an option for wildcard certificates.

We hope that this has answered your questions about how wildcard certificates work. Now, here’s what you need to know to put your new certificate to use.

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Next Steps After Purchasing a Wildcard SSL Certificate

Since they are easier to extend over several subdomains, reduce costs , and are easy to deploy, wildcard SSL certificates could be the perfect fit for quite a few business owners. Once you have decided to use a wildcard SSL, let’s look into what happens next.

  • After purchasing a wildcard SSL certificate, generate a certificate signing request (CSR) with the asterisk before your domain name (for example, *.domain.com).
  • The certificate authority (CA) will then issue an SSL certificate and send it via email with the common name *.domain.com that secures all subdomains at the first level.
  • Follow the installation guidelines and configure your web server correctly to use the certificate
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