In early December 2008, emails were sent to all thawte customers whose certificates are affected by the Debian/OpenSSL vulnerability.
It was discovered that additional recipients of that email do not have certificates generated from, on, or by a Debian-derived OS; however, those recipients do have certificates with key lengths of 512-bits, which thawte regards as weaker than industry-standard. Even though the 512-bit keyed certificates will not be on a revocation program, thawte strongly recommends that those 512-bit keyed certificates are replaced with stronger key pairs.
We recommend that 2048 bit keys are created as 512 bit keys are widely considered to be weak and could, in newer browsers, activate pop-up alerts that will warn internet users that they are connecting to a secure web site that is using weak encryption (see the screen grab below).
This could compromise your digital security and could undermine user confidence in the security being used on your web site.
Therefore, in the interest of better security and the enablement of greater trust, we have decided that 2048 bit keys will now be the minimum suggested strength to be used in the issuance of thawte digital certificates.
Below is the warning you would receive with an Opera browser:
When renewing your thawte digital certificate, you will need to provide us with a new CSR with the same information but with a 2048 bit key length. For instructions on how to generate a new private key and CSR, please follow your specified server software instructions:
Here is a reference document from the RSA Security website: