What is a Wildcard SAN Certificate and How Does It Work?

What is Wildcard SSL?

A Wildcard SSL certificate is a special type of SSL certificate designed to secure a single domain and all of its subdomains.

Unlike regular SSL certificates that only secure one domain, a Wildcard SSL certificate uses a wildcard character (an asterisk, *) in the domain name to allow encryption for any number of subdomains.

This means that with a single Wildcard SSL certificate, a website owner can secure multiple subdomains such as www.example.com, blog.example.com, shop.example.com, and any other subdomains under the main domain (example.com), without the need to purchase individual certificates for each subdomain.

What is SAN/Multi-Domain SSL?

A SAN (Subject Alternative Name) SSL certificate, also known as a Multi-Domain SSL certificate, is an SSL certificate that can secure multiple domain names with a single certificate.

The SAN certificate is ideal for websites, businesses, or organizations that need to secure multiple domains, subdomains, or even multiple types of domain names under a single SSL certificate.

Unlike a Wildcard SSL certificate, which secures only one domain and its subdomains, a SAN certificate allows you to secure several different domain names, whether they are in the same organization or belong to completely different domains. For example, a single SAN certificate could cover:

• example.com
• example.net
• example.org
• blog.example.com
• shop.example.net

What is a Wildcard SAN?

A Wildcard SAN certificate combines the power of both Wildcard SSL and SAN SSL. This certificate enables businesses to secure multiple domains and their subdomains under a single certificate, thereby reducing both the complexity and cost associated with managing multiple certificates.

For example, a Wildcard SAN certificate can cover:

• www.example1.com
• www.example2.com
• mail.example2.com
• blog.example3.net
• *.example3.net (for any subdomains of example3.net)

This provides the flexibility to secure both a wide array of unique domains and their associated subdomains, all under a single certificate.

Working of Wildcard SAN Certificate

A Wildcard SAN Certificate, also known as a Multi-Domain Wildcard Certificate, combines the features of wildcard certificates with Subject Alternative Name (SAN) functionality to secure multiple domains and their subdomains under a single certificate.

The wildcard feature allows the certificate to secure all subdomains of a primary domain (for example, *.example.com covers www.example.com, mail.example.com, etc.), while the SAN feature extends this capability by including additional domains and subdomains explicitly listed in the SAN fields (for example, example.net, api.example.org).

During issuance, the CA will validate ownership for all listed domains and subdomains to ensure full security coverage for these entries.

The server first verifies the requested domain or subdomain against the wildcard entry and the list of SANs when a client connects. It then allows the continuation of the SSL/TLS handshake to set up the secured connection if there is a match.

All first-level subdomains are secured through wildcard entries, whereas securing unrelated domains or subdomains is done explicitly via the SAN entries.

Nevertheless, the certificate does not protect nested subdomains—for instance, sub.api.example.com—under a wildcard.

Although it simplifies the management of SSL in more complex domain structures of enterprises, the certificate must be handled carefully since the same private key is used by all domains, such that if it gets compromised, it could pose serious security risks.

Benefits of a Wildcard SAN Certificate

A Wildcard SAN (Subject Alternative Name) Certificate is an economical SSL/TLS certificate that has the versatility of a Wildcard Certificate along with support for multiple domains and subdomain names all under the one certificate. Here are the key benefits:

Covers Multiple Domains and Subdomains

A Wildcard SAN certificate delivers the option of protecting multiple subdomains of an initial domain using a wildcard. This means that, unlike other systems, it is not necessary to have distinct certificates for each subdomain.

Second, the SAN feature, in addition to the subdomains, lets users add more than one domain name (for example, example.net, example.org) and expand the coverage to more than one domain name.

Thus, it proves to be very useful for any business that maintains several domains and subdomains, securing everything in one certificate.

Cost-Effective

This type of SAN certificate can prove to be less expensive than obtaining different SSL certificates for different subdomains and domains.

Due to the flexibility of the certificate, every subdomain under a wildcard such as *.example.com and several domain names under SAN, businesses are not required to purchase separate certificates for subdomains and domain names.

This kind of approach can be very cost-effective, especially for a large-scale Website or Service that will have numerous sub-domains or domain names.

Simplified Management

Regarding the SSL/TLS certificates, there is inevitably a problem when each domain or a subdomain has its certificate.

Using a Wildcard SAN certificate, all domain-related certificates are comprehensively provided in one certificate, making management easier.

This implies that there is only one certificate to install, renew, and monitor, meaning that there is decreased complication linked with managing many certificates.

Also, it reduces the chance of having misconfiguration and certificate errors, given that there is only a specific certificate to manage.

Flexibility for Growth

The Wildcard SAN certificate gives the possibility to add more subdomains or even additional domain names as a business or website grows, without obtaining a new certificate.

This means that if the network structure or business requirements change, an organization can easily scale up or down without being concerned about obtaining a new certificate.

Businesses can update their current Wildcard SAN certificate to include the new domains, rather than being concerned with obtaining a separate certificate each time a new subdomain or domain is created.

Enhanced Security

A Wildcard SAN certificate ensures that all the domains and subdomains under its coverage are encrypted consistently.

Since there is only one certificate for all your domains and subdomains, there is less chance of misconfigurations that could leave some of your sites unencrypted. This centralization also simplifies the renewal process for keeping all your services secure.

Having a single certificate for multiple domains helps block security gaps that could happen due to different certificates having different expiration dates and different management practices.

Cross-Use Case and TLD Flexibility

Wildcard SAN SSL certificates are quite flexible in that they can protect multiple domains across different top-level domains like .com, .org, .net, or .edu. This is very helpful for businesses that operate differently, have regional domains, or have more than one brand. This type of certificate is perfect for varied requirements if you run an e-commerce site, SaaS, or an enterprise-level site.

Increasing Consumers’ Trust and SEO

An SSL-protected website rises higher in search engine rankings because HTTPS is one of the ranking factors for Google and other search engines. A Wildcard SAN SSL certificate guarantees that all of your domains and subdomains will benefit from this search engine optimization perk.

Moreover, visual indicators of security, such as the padlock icon seen in browsers, help to solidify user trust and confidence that is crucial for e-commerce, SaaS platforms, and online businesses.

Ideal for Big Infrastructures

Enterprise-level web infrastructures usually have a lot of domains, subdomains, and services. A Wildcard SAN SSL certificate is quite appropriate for such an environment. For instance, an enterprise can have regional websites like us.example.com or eu.example.com, service-specific subdomains like support.example.org or partners.example.net, and unrelated domains.

It will make it easier to secure and manage these disparate parts as the infrastructure grows.

Saves Time in Deployment and Maintenance

Installing and maintaining several certificates for multiple domains and subdomains is resource-intensive and time-consuming. A Wildcard SAN SSL certificate consolidates the effort, so IT teams can focus on other more pressing tasks.

A single certificate, about first-time deployment, updates, or renewals, ensures efficiency in all cases while reducing the overhead on operations and ensuring a high level of security.

Example of a Wildcard SAN Certificate

Imagine a company named TechDemo that owns the following domains and subdomains:

• www.techdemo.com
• shop.techdemo.com
• blog.techdemo.com
• mail.techdemo.net
• www.itservices.techdemo.edu

Without a Wildcard SAN certificate, TechGlobal would need to buy:

• A Wildcard SSL for *.techdemo.com (to secure the subdomains)
• A SAN certificate for mail.techdemo.net
• A SAN certificate for www.itservices.techdemo.edu

However, with a single Wildcard SAN certificate, you can secure all of the above domains and subdomains and add many more domains. This reduces the need for multiple certificates and ensures that all traffic to and from their sites is encrypted with a single solution.

Wildcard Vs SAN SSL: Short Summary

Here’s a detailed comparison between Wildcard SSL and SAN SSL certificates in table form:

Feature	Wildcard SSL Certificate	SAN SSL Certificate (Multi-Domain SSL)
Purpose	Secures a single domain and all subdomains at one level.	Secures multiple domains and/or subdomains (can be unrelated).
Domains/Subdomains Covered	One domain and its subdomains (e.g., *.example.com for example.com).	Multiple domains and subdomains explicitly listed in the certificate.
Flexibility	Automatically secures newly created subdomains without reissuing.	New domains/subdomains must be explicitly added and require certificate reissuance.
Example Use Case	– *.example.com covers blog.example.com, mail.example.com	– example.com, example.org, mail.example.net, shop.example.com
TLDs Supported	Limited to one domain and subdomains under the same TLD (e.g., .com).	Can include different domains with different TLDs (e.g., .com, .net, .org).
Level of Subdomains Covered	Secures one level of subdomains (e.g., *.example.com but not sub.mail.example.com).	Can secure specific subdomains, such as sub.mail.example.com, but each must be listed.
Cost	Cost-effective for securing multiple subdomains under one domain.	More expensive, especially for many unrelated domains.
Certificate Management	Easier to administer because it applies to all subdomains automatically.	More complex, as each domain/subdomain must be explicitly listed.
Private Key Sharing	All subdomains share the same private key, creating a possible security issue if one subdomain is compromised.	Each domain/subdomain has its own explicit listing, improving security management.
Scalability	Recommended for only a single domain at the subdomain level; only one level is covered.	Highly scalable for unrelated domains and subdomains.
Reissuance Requirements	Does not apply when adding subdomains.	Required when adding new domains/subdomains.
Wildcard Support	Secures one wildcard either  (e.g., *.example.com) for each certificate.	Can optionally include wildcards in SAN entries (e.g., *.example.com, *.example.org).
SSL Type	Single-domain Wildcard SSL.	Multi-domain SAN (UCC) SSL.
Use Case Scenarios	– Organizations with numerous subdomains under one domain..	– Companies managing multiple domains or brands.
Compatibility	Supported by most browsers and servers.	Supported by most browsers and servers but may require SAN support in older systems.
Certificate Authority (CA)	Most CAs issue Wildcard SSL certificates.	Most CAs issue SAN SSL certificates with a limit (e.g., 250 domains).
Best For	Securing subdomains under a single domain.	Securing multiple unrelated domains and subdomains.

Conclusion

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