Re: [openpgp] Context Parameters for Signing and Encryption

Falko Strenzke <falko.strenzke@mtg.de> Tue, 07 February 2023 12:14 UTC

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From: Falko Strenzke <falko.strenzke@mtg.de>
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Subject: Re: [openpgp] Context Parameters for Signing and Encryption
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I briefly looked into 
https://www.nds.ruhr-uni-bochum.de/media/nds/veroeffentlichungen/2020/12/06/schwenk2020.pdf

As I understand, the mitigation they propose will lead to false 
positives under certain circumstances, depending on on involved MTAs. 
"We evaluated how eleven popular email service providers [...]". Is this 
really sufficient? I am far from being an expert in mail delivery, but 
in my understanding any commercial or self-hosted MTA could have a 
different effect on their countermeasure, potentially leading to false 
positives. False positives here seems to mean an undecipherable message 
arriving at the recipient.

Has someone looked into how far the context parameters that OpenPGP 
would support would be affected by this? In my opinion, a false positive 
rate > 0 would be unacceptable and probably lead to clients not 
implementing that feature.

Maybe someone with a greater understanding of this topic can elaborate 
on this.

- Falko

Am 05.02.23 um 18:23 schrieb Daniel Kahn Gillmor:
> Hi folks --
>
> we need to resolve whether there will be a context parameter added to
> the crypto-refresh, for signing, and for encryption.  i'd like folks to
> be clear aobut whether they're talking about signing or encryption, but
> we can use this thread for both.
>
> The mechanisms and use cases for signing and encryption are likely to be
> different.
>
> Seehttps://gitlab.com/openpgp-wg/rfc4880bis/-/issues/145  and earlier
> discussion on this list for background.
>
> The main questions:
>
> - Should we provide a context parameter for signing for v5 signatures?
>
> - Should we provide a context parameter for encryption for v2 SEIPD
>    packets?
>
>
> Interesting subquestion for either of the above:
>
> - if so, how do we specify or register the context parameter for
>    different use domains of use?  How do we even define these different
>    "domains"?
>
> An MR that says "yes, add a context parameter for both" and "don't specify any
> specific context or set up a registry for either" is at:
> https://gitlab.com/openpgp-wg/rfc4880bis/-/merge_requests/214
>
> Please use this thread for this discussion, but remember to clarify
> whether you're thinking/talking about signing and encryption.
>
>          --dkg
>
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-- 

*MTG AG*
Dr. Falko Strenzke
Executive System Architect

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E-Mail: falko.strenzke@mtg.de
Web: mtg.de <https://www.mtg.de>


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