On Mon, Oct 30, 2023 at 8:20 AM Ilari Liusvaara <[email protected]>
wrote:

> On Mon, Oct 30, 2023 at 07:55:09AM -0600, Brian Campbell wrote:
> > On Tue, Oct 24, 2023 at 4:46 AM Ilari Liusvaara <
> [email protected]>
> > wrote:
> >
> > > And another is why Direct Encryption REALLY SHOULD NOT be used.
> > >
> >
> > Can you say more about why? This is one I don't recall having seen
> > much discussion/criticism about.
>
> Basically, none of the algorithms is suitable for that. Either the
> algorithm has nonces that are too small, or is not meant for bulk
> encryption.
>
> For algorithm to be suitable for direct encryption, one would need
> algorithm meant for bulk encryption that is either MRAE or has
> large nonces. There are none currently.
>

Are the AES_CBC_HMAC_SHA2 Algorithms
<https://datatracker.ietf.org/doc/html/rfc7518#section-5.2> in JWE unsafe
with Direct Encryption? I guess that asking the question does suggest that
more guidance would be useful. But I've generally assumed that it was okay.
JWA does kinda mention nonce/IV reuse and limiting the number of
invocations in its AES GCM Security Considerations
<https://datatracker.ietf.org/doc/html/rfc7518#section-8.4> but that's only
about GCM.



> The problem does not extend to modes with KDF, because the KDF makes
> things behave like there was a large nonce.
>
>
>
>
> -Ilari
>
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