What is an SAN Certificate?

An SAN (Subject Alternative Name) Certificate, also known as a multi-domain SSL certificate, is a type of SSL/TLS certificate that allows multiple domain names to be protected by a single certificate. SAN certificates are ideal for businesses and organizations that manage multiple websites or subdomains, as they simplify SSL management by consolidating domains under one certificate.

1. Understanding SAN Certificates

SAN Certificates were created to streamline SSL security for complex network environments. Unlike standard SSL certificates, which protect only a single domain, SAN certificates support multiple domain names or subdomains, allowing flexibility in coverage. For example, a single SAN certificate can protect:

• www.example.com
• mail.example.com
• shop.example.org
• app.example.net

This capability is particularly useful for large organizations, SaaS applications, and e-commerce websites that maintain multiple sites or services.

2. Benefits of Using an SAN Certificate

• Cost Efficiency: Instead of purchasing and managing separate certificates for each domain, a single SAN certificate covers multiple domains, saving costs.
• Simplified Management: Managing one certificate for multiple domains reduces administrative overhead.
• Enhanced Security: With one certificate handling multiple domains, organizations can streamline their SSL implementation without sacrificing security.
• Improved Compatibility: SAN certificates support multiple domain configurations, making them compatible with most web and mail servers.

3. How SAN Certificates Work

SAN certificates contain additional fields, known as “Subject Alternative Names,” within the certificate structure. When issued, the certificate includes each specified domain in these fields, allowing browsers and servers to validate SSL for each domain listed.

Example of SAN Configuration

• Primary Domain (Common Name): www.example.com
• SAN Domains: blog.example.com, shop.example.org, secure.example.net

This flexibility means that changes to subdomains or additional domains can often be managed within the certificate, depending on the certificate authority’s policies.

4. Types of SAN Certificates

• Multi-Domain SSL Certificate: Protects multiple domains with different TLDs (e.g., .com, .net).
• Wildcard SAN Certificate: Covers multiple subdomains of specified domains, using a wildcard character (e.g., *.example.com).
• EV (Extended Validation) SAN Certificate: Provides the highest validation level, showing the verified organization name in the browser’s address bar for all listed domains.

5. How to Obtain an SAN Certificate

To acquire an SAN certificate, follow these steps:

1. Select a Certificate Authority (CA): Choose a trusted CA that offers SAN certificates.
2. Specify SAN Domains: During the application, list the domains and subdomains you wish to protect.
3. Complete Domain Validation: Verify ownership for each domain listed in the SAN field, typically through email, DNS, or file-based validation.
4. Install the Certificate: Once issued, install the certificate on your server. Configure each listed domain to use the SAN certificate.

6. Managing and Renewing an SAN Certificate

Renewal and management of SAN certificates are essential to maintain security. When renewing:

• Review the list of domains for accuracy.
• Ensure that any additional domains or subdomains are updated with the CA.
• Install the renewed certificate on your server promptly to avoid security warnings.

7. Common Uses of SAN Certificates

• Web Applications: SaaS providers often use SAN certificates to secure multiple services under different domains.
• Enterprise Networks: Corporations with a mix of subdomains and separate domain names use SAN certificates to streamline SSL security.
• E-commerce Sites: Businesses with multiple regional sites can use SAN certificates to secure each site without needing separate certificates.

Conclusion

SAN Certificates offer a versatile, efficient solution for securing multiple domains with a single certificate. Their flexibility makes them an excellent choice for businesses managing multiple web services, while their cost and time-saving benefits make them ideal for any organization looking to simplify SSL security.