In the cybersecurity field, SSL/TLS certificates provide confidentiality, integrity, and authenticity of data that is transferred between clients and servers. Trusted organizations referred to as certificate authority authenticate websites so that any secured connection can take place.
Many businesses and organizations question whether you can have more than one Certificate Authority (CAs) on just one domain. In this article, we take a deep look into it and give you a deep understanding of the whole process about the implications, best practice, and managing a single multiple CAs domain.
What is a Certificate Authority (CA)?
A Certificate Authority is an entity that issues SSL/TLS certificates for use in encrypting exchanged data between the browser of a user and that of a server. It thus provides validation of an identity in a corresponding secure connection to establish the authenticity of the website.
Sites having HTTPS in the URL would make the browser cross-check with an SSL/TLS certificate ensuring that it has been provided by a trusted CA. Importantly, an intruder cannot intercept the transmitted data so that he is unable to alter it.
Can You Have Two Certificate Authorities on One Domain?
Yes, two different Certificate Authorities can be placed within one domain, but usually such a scenario involves using multiple SSL/TLS certificates from different CAs. This can be applied for the following purposes:
Use of EV and DV Certificates
One way to have two CAs on one domain is by using an EV certificate from one CA for your main domain and a DV certificate from a different CA for a subdomain. This allows you to meet different validation and trust requirements depending on the sections of your web site.
Separate Certificates for Different Usages
The third is where one uses different CAs for different services or applications under the same domain. For example, you might have one certificate from a CA for website SSL and another from a different CA for email encryption. This separation of certificates can improve security for distinct services running on the same domain.
Cross-signing
Sometimes, a certificate issued by one CA has to be cross-signed by a different CA to ensure broader recognition, especially in the case of legacy systems. Cross-signing ensures the older systems trust newer ones or less recognized CAs, in turn ensuring continuity and avoiding possible compatibility issues.
Although these configurations are possible, the certificates must be handled with care to avoid conflicts, since browsers expect to see only one valid certificate for a specific domain or subdomain.
Multiple Subdomains, Multiple CAs
In case your domain has more than one subdomain (e.g., www.example.com, blog.example.com, shop.example.com), then you can use a different CA for each of the subdomains. In many places in your website, you have the freedom to control the security.
For instance:
- www.example.com could use a certificate from CA1.
- blog.example.com could use a certificate from CA2.
This approach may be helpful if you have specific subdomains that require specialized security requirements or if your organization uses multiple CAs for different departments or services.
Using a Multi-Domain (SAN) SSL Certificate
A SAN certificate is an SSL certificate that enables you to secure multiple domain names and subdomains under one certificate. You can have different CAs for each domain or subdomain listed under the SAN certificate.
This feature enables you to have more than one domain or subdomain to share a certificate. You can assign a different CA for each one, if needed. However, this is a more complicated procedure that needs careful configuration to avoid compatibility issues.
Load Balancing and Multiple CAs
For high-traffic web sites or large organizations, load balancing is the rule of thumb to distribute incoming traffic to various servers. In this situation, each server in a load-balanced environment might need its own SSL/TLS certificate, issued by potentially different CAs.
It can help optimize performance and redundancy but requires careful planning to ensure the certificates work seamlessly across all the servers.
Why Would You Have Two Certificate Authorities on One Domain?
Although it is easily feasible to have two or more CAs for the same domain, you could probably ask why you may need to do this at all. Here are several reasons why businesses and organizations do so:
It Can Increase Compatibility
Different Certificate Authorities could have a different level of acceptance by different browsers, devices, or operating systems. Some may not accept some newer CAs because those are quite old or highly specialized. Using certificates issued by various CAs assures that everyone can access your site regardless of the browser used or even the device and operating system.
Redundancy and Backup
Using multiple CAs can provide redundancy in case one CA’s certificate is revoked, expires, or is compromised. This ensures that there is no downtime or disruption in service for your website visitors, as another certificate can take over.
Security Requirements
Some organizations may use different CAs for different purposes. For instance, one CA may offer advanced features, such as Extended Validation (EV) certificates, providing a higher level of trust, while another CA might be more cost-effective options for other subdomains.
Regulatory Compliance
Some industries or nations require usage of specific CAs because of regulatory standard compliance requirements. Using a multiple-CAs setup could help make sure that all domains for your website align with needed compliance standards. 5. Trust and Brand Recognition
Other CAs have more enhanced recognition or trust level in their certificates, for instance, EV certificates. Therefore, if you would want to show more trust on your visitors, then using a well-known CA to your specific subdomains can be a choice; examples are your main website and online store.
How to Implement Two CAs on One Domain
If you’ve decided that using two CAs on your domain is the best choice for your business, here’s how to implement it:
- Obtain SSL Certificates from Different CAs
You’ll have to obtain SSL/TLS certificates from two separate CAs. You’ll need to ensure that the CA you choose supports your security requirements and that the certificates it issues support the web servers and browsers you’re trying to protect.
- Install the Certificates on Your Web Server
Each SSL certificate must be installed on your web server. The installation process will depend on the software you are using for your web server (for example, Apache, Nginx, IIS). Make sure that you configure the server to serve the appropriate certificate for each domain or subdomain.
- Test for Compatibility
After installing the certificates, test them for compatibility with other browsers and devices using SSL tools such as SSL Labs’ SSL Test. Verify that both certificates are installed correctly and that your website is accessible to all users.
- Monitoring and Management of Expiration Dates
Track expiration dates for each certificate so that they can be renewed on time. You would also take care of proper handling of any possible certificate revocation so that services are not interrupted.
Also Read: Does ASE Certification Matter for a Small Business?
Conclusion
One may have two Certificate Authorities on the same domain. It can be quite useful for certain applications where one wants compatibility with other browsers, redundancy, or certain security needs. However, the management of multiple CAs must be done carefully so that the potential issues associated with configuration, compatibility, or certificate management are not raised.
By understanding the process and considering the reasons behind using multiple CAs, you can ensure a secure and reliable web presence for your domain, which will give your users peace of mind while maintaining trust and compliance.
FAQs
Can I use two different SSL certificates on the same server?
Yes, it is possible to use two different SSL certificates on the same server. One can configure a web server to service different certificates for different domains or subdomains.
Does having two CAs increase the security level of my website?
Using two CAs doesn’t necessarily increase your website’s security. Security is more dependent on the strength of the encryption and the type of certificate (e.g., EV, DV, or OV). Multiple CAs may provide redundancy or compatibility but won’t inherently improve security.
Can I use multiple CAs for a multi-domain certificate?
Yes, it is possible to use a multi-domain (SAN) certificate with certificates issued by different CAs. However, this is a more complex setup and needs to be carefully managed in order not to have problems with compatibility.
What happens if one of my CAs is compromised?
In the case of a compromised CA, you should replace the certificate at once and consider changing CAs for that domain or subdomain. You should ensure redundancy in place for minimal disruption.
Can I mix free and paid SSL certificates from different CAs?
Yes, you can combine free and paid SSL certificates from different CAs. However, make sure the free certificate is reliable to meet your security requirements, and it should also support your web server as well as your users’ browsers.