Re: [therightkey] Updated Certificate Transparency + Extended Validation plan

[Ben Laurie <[e-mail]>]

On 11 February 2014 00:59, Rick Andrews <[e-mail]> wrote:
>> -----Original Message-----
>> From: therightkey [mailto:[e-mail]] On Behalf Of
>> Ben Laurie
>> Sent: Saturday, February 08, 2014 5:40 AM
>> To: Adam Langley
>> Cc: [e-mail]; certificate-transparency; CABFPub
>> Subject: Re: [therightkey] Updated Certificate Transparency + Extended
>> Validation plan
>>
>> On 6 February 2014 19:05, Adam Langley <[e-mail]> wrote:
>> > On Thu, Feb 6, 2014 at 1:51 PM, Rick Andrews
>> <[e-mail]> wrote:
>> >> Can you clarify something? The SCT delivery options described in the
>> RFC are options for the web site owner, not for the CA. CAs will need
>> to support all three options. We will have customers who won’t do
>> stapling and can’t handle TLS extensions, so they just want the SCTs
>> embedded in the cert. But not all customers will prefer that option. I
>> believe other customers will want the SCT-in-the-OCSP-response or TLS
>> extension option, because in those options you don’t have to transmit
>> the SCTs in every SSL handshake. I suspect some of our large customers
>> who are obsessed with performance will demand one of these options.
>> >>
>> >> So CAs will need to support all three options, unless you’re so
>> small a CA that your few EV customers agree on one option. Is that your
>> expectation?
>> >
>> > SCTs embedded in the certificate won't be sent for resumption
>> > handshakes of course.
>> >
>> > The TLS extension will be sent in the same cases as SCTs embedded in
>> > the certificate. (And the TLS extension doesn't need the CA to do
>> > anything.)
>
> I thought the TLS extension will be sent only if the client requests it. 'Clients that support the extension SHOULD send a ClientHello extension with the appropriate type and empty "extension_data".'

That is true, but I would expect all CT-capable clients to support the
extension.

> And I suspect that CAs would need/want to create a service to help their customers obtain SCTs if they choose the TLS extension option.

Sure.