Re: [TLS] SCHC for DTLS

[Robert Moskowitz <[e-mail]>]

Greetings Hannes,

This is for the record layer.  And I really don't know how much would be 
gained.

But as I would see it, this use of SCHC would be for UDP/DTLS/cipher.  
Since it is starting with UDP, SCHC would have to be an IP Protocol (not 
currently defined as such).  So you loose 1 byte for the SCHC rule, 
against the 8 probably saved in compressing UDP to 0 bytes.  Then there 
is the cipher.  Try AES-GCM-12; what is currently used for the IV?  Can 
something like rfc8750 be added to use the seq # in the DTLS header and 
gain maybe 16 bytes?  I really don't know the DTLS header at all.  I 
have tried to find some decent layout as I am use to for ESP in 4303 
(Fig 1) for side-by-side comparison.

But if it means being able to fit over some UHF carrier for unmanned 
aircraft (UA) Network Remote ID (Net-RID) and Command and Control (C2)?  
Worth the effort.

So this is not something I could do myself, but something that I see 
using and thus pitching in on doing it.

On 5/30/22 05:33, Hannes Tschofenig wrote:
>
> Bob, is this about compressing the DTLS record layer or the DTLS 
> handshake protocol?
>
> For the former, I wonder how much is there actually to compress (when 
> using DTLS 1.3)?
>
> *From:* TLS <[e-mail]> *On Behalf Of * Eric Rescorla
> *Sent:* Friday, May 27, 2022 5:30 PM
> *To:* Robert Moskowitz <[e-mail]>
> *Cc:* <[e-mail]> <[e-mail]>
> *Subject:* Re: [TLS] SCHC for DTLS
>
> On Fri, May 27, 2022 at 6:27 AM Robert Moskowitz 
> <[e-mail]> wrote:
>
>     Is there any activity to define SCHC rules for DTLS?
>
> Not to my knowledge.
>
> -Ekr
>
>
>     I want this for Unmanned Aircraft (UA) Network Remote ID (Net-RID)
>     communications from the UA to the Net-RID Service Provider (SP).
>
>     See
>
>     https://datatracker.ietf.org/doc/draft-moskowitz-drip-secure-nrid-c2/
>
>     I am compressing ESP traffic using rfc 8750 and:
>
>     https://datatracker.ietf.org/doc/draft-mglt-ipsecme-diet-esp/
>
>     SCHC is negotiated in IKE (and will be in HIP) and SA tables allow
>     the
>     ESP receiver to recognize a SCHC compressed ESP Header and act
>     properly.
>
>     It is not so simple with DTLS.  First UDP is below DTLS, so how do
>     you
>     compress it?  The way I see it, SCHC would need to be assigned an IP
>     Protocol type so that the transport processing can start right up
>     with
>     the SCHC rule for UDP and then on to DTLS and then the cipher.
>
>     Or at least how I see the challenge.
>
>     So I am looking for any extant work on SCHC for DTLS and/or
>     interest in
>     this activity.
>
>     The CoAP SCHC work, rfc 8824, dodge DTLS compression. Or that is
>     how I
>     read it.
>
>     Thanks
>
>     Bob
>
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