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Revise certificate

hi this is Paul Turner with benefit and today what we're going to talk about is how a certificate gets validated something commonly called chain validation if you remember in another session we actually walked through how certificates get issued all the way from the root CA to a CA certificate all the way to the server certificate for ABCD comm now what we're going to look at is if we've got a user connecting with a browser and they want to connect up to abc.com when they connect up they're going to do that with a secure protocol called HTTPS this goes over TLS when the server receives this request it's going to turn around it's going to return its certificate as well as any CA certificates that are chained to that meal you'll understand that in just a moment these are the certificates that that browser is going to use to validate that it's actually talking to the correct server to the server that it wants to be talking to so it opens these up and it says ok I connect it up to ABCD comm let me look here yep this certificate was issued to abc.com and I want to check to make sure it's still valid the expiration date hasn't expired yet this is the expiration date it's called valid - in certificate terms and now what it says is ok now this was issued by CA 1 I want to make sure that in fact I you know that I trust CA 1 so let me look at what other certificates I've got oh here's a certificate that is issued the CA 1 it's still valid so I checked the date for that but it was issued by but-- CA and and i didn't receive any other certificates if you see my session on what is a PKI what you'll remember is that each browser each system will hold a set of certificates trusted CAS that it's going to use to validate certificates and so it goes into its the little trust store and it looks and says is there a certificate for root CA and lo and behold at books and says hey I've got one here this is a certificate that I've got installed on my software that I trust it was it's a root certificate issued by root CA to itself and it's got a public key in here first of all this is still valid it checks that the date I mean and then the next thing it does it says okay I've got this public key what I'm going to do is I'm going to use this public key to validate the signature on this certificate and make sure that this is a valid signature now it says okay now I trust everything within this certificate because it was signed by somebody who I trust so it looks at this and says okay this was ca1 certificate let me see...