Google to revoke trust in a Symantec root certificate

The announcement comes after Symantec unveiled plans to retire the Class 3 Public Primary Certification Authority from public use. This is a widely trusted CA that it acquired along with Verisign's SSL business in 2010.

In an alert, the company said that as of Dec. 1, it no longer was using the root certificate, which is trusted by default in most browsers and operating systems, to issue TLS/SSL or code signing certificates.

The company advises owners of digital certificates that chain back to the Class 3 Public Primary CA to obtain new ones that link back to a more modern root. Such replacement certificates are available for free.

According to Google, Symantec will not completely kill off the Class 3 Public Primary CA root and intends to use it for new, unspecified purposes. Because of this, the browser maker cannot guarantee that non-public certificates issued under this root in the future won't be used to "intercept, disrupt, or impersonate the secure communication of Google’s products or users."

"As Symantec is unwilling to specify the new purposes for these certificates, and as they are aware of the risk to Google’s users, they have requested that Google take preventative action by removing and distrusting this root certificate," said Ryan Sleevi, a Google software engineer, in a blog post.

The company will remove two versions of the Class 3 Public Primary CA certificate from its products' trust lists. One version is signed with SHA-1, a hashing algorithm that is in the process of being phased out, and one is signed with MD2, an even older hashing function. Both versions were issued in 1996 and are set to expire in 2028.

According to Google, Symantec doesn't believe that any of its customers who operate HTTPS websites, or their users, will be impacted. However, in its own advisory Symantec acknowledges that users might receive errors in the future if they try to access websites whose certificates chain back to the distrusted root.

This might also happen with signed applications if OS makers also start removing the Class 3 Public Primary CA certificate from their trust lists. Therefore developers should also change their certificates if their chain back to this root and re-sign their code.