>
> (HPKE is both bulk and aad capable, so it is its own class in COSE,
> not Key Transport class. This also gives it correct properties w.r.t.
> sections 5.3 and 5.4.)


Under the premise of prohibiting the use of AE algs at layer0 and using
HPKE algs for key wrapping at layer1,  should we really introduce next_alg?

I just want to understand the reason correctly.

Daisuke

2024年3月19日(火) 4:03 Ilari Liusvaara <[email protected]>:

> On Mon, Mar 18, 2024 at 05:31:34PM +0000, lgl island-resort.com wrote:
> >
> > On Mar 18, 2024, at 6:05 AM, AJITOMI Daisuke <[email protected]> wrote:
> >
> > What I think should be done is to prohibit using non-authenticated
> > content encryption and key wrap algorithms in COSE.
> >
> > I agree. In the COSE-HPKE draft, we should stop supporting legacy
> > non-AEADs and offer the simplest and safest solution.
> >
> > Even if the WG agrees to prohibit non-AEADs, I think we should get rid
> > of COSE_KDF_Context and should authenticate the algorithm ID across
> > layers with a new Enc_structure.
>
> RFC9052 explicitly defines both AE (section 5.4) and AEAD (section 5.3)
> ciphers. What is obviously intended is that all symmetric ciphers are
> authenticated.
>
> This causes really nasty issues with algorithm binding:
>
> AE algorithms have no Enc_structure, making it difficult to bind the
> algorithms. Worse, all the pre-composed KAwKW algorithms are AE.
>
> Then to make matters even more complicated, Key Transport class is
> not aad capable. That also causes major issues with binding.
>
> (HPKE is both bulk and aad capable, so it is its own class in COSE,
> not Key Transport class. This also gives it correct properties w.r.t.
> sections 5.3 and 5.4.)
>
>
>
>
> -Ilari
>
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