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Re: [TLS] TLS v1.2 performance (was Re: TLSv1.2 with DSA client

Martin Rex <mrex@sap.com> Fri, 04 March 2011 21:26 UTC

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From: Martin Rex <mrex@sap.com>
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To: mike-list@pobox.com
Date: Fri, 04 Mar 2011 22:27:44 +0100
In-Reply-To: <4D714887.6060003@pobox.com> from "Michael D'Errico" at Mar 4, 11 12:16:07 pm
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Subject: Re: [TLS] TLS v1.2 performance (was Re: TLSv1.2 with DSA client
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Michael D'Errico wrote:
> 
> Matt DeMoss wrote:
> > I'd encourage consideration of client certificates also. If the client
> > has certificate chains for SHA1 and SHA2 or for SHA2 and SHA3, it
> > needs a way to choose which chain to send during periods of transition
> > where some servers will reject SHA2 and others will reject SHA3.
> 
> Isn't this already in TLS 1.2?  When the server requests a client
> certificate, the CertificateRequest includes a list of acceptable
> signature algorithms.  The client can then check each of its
> certificate chains to find the best one the server can handle.

It is *MUCH* worse than that.

TLSv1.2 goes as far as _requiring_ that if the signature_algorithm
extension is sent, that the receiver MUST ensure that all certificates
in the chain are from the signature_algorithm set.

That is not just shooting yourself in the foot, that is shooting
"the whole nine yards" (the entire ammunition belt) in your foot.

-Martin

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