# What does “G2” mean when used with X509 certficates and certificate authorities?

For example "Google Internet Authority G2"?. I thought it was another way of specifying Class 2 (for organizations, for which proof of identity is required) but then see certificates such as "VeriSign Class 3 Public Primary CA - G2".

It couldn't be something so simple such as Generation 2 could it? Hope someone who woks for a CA can explain these naming conventions. Thanks in advance.

• I don't work for a CA, but yes it is "generation". Verisign, I believe the oldest public CA operating under its original name (though now owned by Symantec), is up to G5. Note that some generations were replaced "early" because of developments like MD5 being broken for collision, SHA1 and RSA1024 being threatened, and ECC becoming more popular. "Class" generally means either validation (as you note) or application (SSL vs email vs codesigning etc). – dave_thompson_085 Sep 12 '14 at 5:14
• There are also other identifiers like X1 or R1 and E1. Those then are types and a generation or alternative counter. But it is just a text, there is IMHO no standard or automated meaning to it in X509 – eckes May 11 '17 at 2:48

• G3 - sha256WithRSAEncryption
• G4 - ecdsa-with-SHA384