Subject: [TLS] Signature Algorithms Extension Clarification

From: Hannes Tschofenig <[email-masked]>
Date: Thu, 22 Sep 2016 11:33:13 +0200

Hi all,

I need a clarification regarding the use of the signature algorithms.

Reading Section 4.2.3. "Signature Algorithms" I got the impression that 
there is a new extension being defined called 
'supported_signature_algorithms', which replaces the previous 
'signature_algorithm' extension.

The difference between the 'signature_algorithm' extension in RFC 5246 
and the newly defined 'supported_signature_algorithms' extension is that 
the new extension only contains the digital signature algorithm and not 
the hash function anymore.

If that's indeed the intention I would prefer if the text uses the 
'supported_signature_algorithms' rather than 'signature_algorithms'.
(as it is done in Section 4.4.2. "Certificate Verify"). Unfortunately 
the term 'signature_algorithms' is used in many other places in the 
document itself, including the IANA consideration section that makes a 
reference to RFC 5246.

Is it correct that the 'supported_signature_algorithms' extension 
replaces the 'signature_algorithm' extension from RFC 5246?

Ciao
Hannes

---

From: Eric Rescorla <[email-masked]>
Date: Thu, 22 Sep 2016 05:30:43 -0700

On Thu, Sep 22, 2016 at 2:33 AM, Hannes Tschofenig <
[email-masked]> wrote:

> there is a new extension being defined called 'supported_signature_algorithms',
> which replaces the previous 'signature_algorithm' extension.
>
> The difference between the 'signature_algorithm' extension in RFC 5246 and
> the newly defined 'supported_signature_algorithms' extension is that the
> new extension only contains the digital signature algorithm and not the
> hash function anymore.
>

> (as it is done in Section 4.4.2. "Certificate Verify"). Unfortunately the
> term 'signature_algorithms' is used in many other places in the document
> itself, including the IANA consideration section that makes a reference to
> RFC 5246.
>

Yes and no :)

We've redefined the structure to be "signature and hash and curve in one
code point" but we're just
retconning the existing values and extension code point.

-Ekr

> Ciao
> Hannes
>
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