Presumably you refer to this talk? 
https://talks.secworkshop.events/osw2026/talk/JUEELE/

Can you share slides for it? It would be helpful to understand why this is 
needed and why the proposed shortcomings cannot be addressed by DPoP itself (eg 
via an update) rather than an entirely different approach.

At present I oppose adoption for several reasons:

i. We already have DPoP (and mTLS), and this draft provides no rationale itself 
as to why it is not sufficient. Adding yet another POP mechanism will only harm 
interop. Any call for adoption is premature until the rationale is clearly 
stated.

ii. Signatures generally have numerous problems, including severe unintended 
consequences. One of the drawbacks of DPoP you mention is that it doesn't sign 
the message content, but for me this is a considerable advantage. Signing 
users' messages without their explicit informed consent is IMO actively harmful 
to the Internet ecosystem, as evidenced eg by this article by Matthew Green on 
the harms of DKIM signatures: 
https://blog.cryptographyengineering.com/2020/11/16/ok-google-please-publish-your-dkim-secret-keys/
 . I don't really see any reasonable way to mitigate this risk other than to 
not include the message content in the signature, but this is apparently a key 
motivating use-case. Therefore I cannot support the proposal. (I provide more 
technical reasons against signatures as an authentication mechanism in 
https://neilmadden.blog/2024/09/18/digital-signatures-and-how-to-avoid-them/).

iii. HttpSig in particular brings in a whole load of new machinery that OAuth 
implementations will have to know about, including more IANA registries, and 
another new ad-hoc public key representation format. It repeats security 
mistakes of the past, such as canonicalisation and allowing (if not mandating) 
an attacker-asserted "alg" parameter. The bar should be very high for 
introducing a new PoP mechanism, especially one of this complexity. I don't 
think this draft meets that bar.

Neil

> On 22 Sep 2026, at 15:38, Paul Bastian <[email protected]> wrote:
> 
> I support the adoption. 
> 
> We have a stable HTTP message signature specification now and people 
> deploying DPoP have realized a number of shortcomings that Christian and I 
> presented about at the OAuth Security workshop last time. 
> 
> Paul
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