[lamps] Re: TLS Client Certificates; a survey

[Nico Williams <[e-mail]>]

On Mon, Mar 23, 2026 at 02:00:35PM -0400, Michael Richardson wrote:
> Salz, Rich <rsalz=[e-mail]> wrote:
>       > Since WebPKI CA’s will not be able to issue TLS-Client certificates,
>       > what are the customers and CAs thinking of doing?
> 
> You say this as if it's a new thing :-)

well, it's recent.  It happened around October 2025.

> Is it the "change" that certificates obtained for code signing or email use
> will have the tls-kp-clientAuth EKU ommitted?

The change is that roots in the Chrome Root Program may not sign
intermediates that sign any EE certificates having any EKUs other than
id-kp-serverAuth.  A CA can still have roots outside the CRP that do
sign intermediates that do sign non-server EE certificates, but probably
few will.

>     > Replies to be will be summarized to both lists. Please be careful if
>     > you use reply-all.
> 
> 1. This assumes the RP are checking EKU.

Yes, but they should.

> 2. I think 94% of usage of mTLS is via private PKI for the client side.

Probably true.  The two applications I know to be affected are XMPP and
SMTP.

Nico
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