What is a Single Root SSL Certificate?

When connecting to a webserver over SSL, the visitor's browser decides whether or not to trust the website's SSL certificate based on which Certification Authority (CA) has issued the actual SSL certificate. To determine this, the browser looks at its list of trusted issuing authorities - represented by a collection of Trusted Root CA certificates added into the browser by the browser vendor (such as Microsoft and Netscape).

Most SSL certificates are issued by CAs who own and use their own Trusted Root CA certificates, such as those issued by GeoTrust, RapidSSL, Thawte, Globalsign, Digicert, Verisign. As these CAs are known to browser vendors as a trusted issuing authority, their Trusted Root CA certificate has already been added to all popular browsers, and hence is already trusted. These SSL certificates are known as "single root" SSL certificates. Inmost cases the certificates appear in the name of the CA. In the case of RapidSSL.com, a subsidiary of GeoTrust, GeoTrust owns the Equifax root used to issue its certificates.

Some Certification Authorities do not have a Trusted Root CA certificate present in browsers, or do not use the root they do own, and use a "chained root" in order for their SSL certificates to be trusted - essentially a CA with a Trusted Root CA certificate issues a "chained" certificate which "inherits" the browser recognition of the Trusted Root CA. These SSL certificates are known as "chained root" SSL certificates.

Installation of chained root ssl certificates are more complex and some web servers and applications are not compatible with chained root ssl certificates.

For a Certification Authority to have and use its own Trusted Root CA certificate already present in browsers is a clear sign that they are long-time, stable and credible organizations who have long term relationships with the browser vendors (such as Microsoft and Netscape) for the inclusion of their Trusted Root CA certificates. For this reason, such CAs are seen as being considerably more credible and stable than chained root certificate providers who do not have a direct relationship with the browser vendors, or do not use their own root certificates to issue SSL certificates.

You can view the Certification Authorities who have and use their own root certificates by viewing the list in your browser.

Chained root certificates require additional effort to install as the webserver must also have the chained root installed. This is not necessary for single root certificates.

TruePersona™ recommends the use of single root SSL certificates.