Subject: [Ace] DCAF implementation size numbers

From: Carsten Bormann <[email-masked]>
Date: Tue, 13 Jan 2015 18:39:51 +0100

Thanks to Eve Maler for the interesting Webinar we had today.
It is refreshing to see that the separation between requesting party and
resource owner comes up in the OAuth environment as well.
I'm looking forward to a decaffeinated OAuth -- we should just make sure
we bridge the gap and don't fill it in...

I promised to provide some DCAF numbers.

>From http://dx.doi.org/10.1109/ICNP.2014.104 (slides at
http://netsec.cs.uoregon.edu/npsec2014/slides/dcaf_npsec2014.pdf -- see
slide 24):

> A prototypical implementation for an ARM Cortex M3 (CC2538) shows that
> DCAF adds about 440 Bytes of code and 54 Bytes of data plus storage
> for the Ticket Face to an existing CoAP server with DTLS support.

(No, these are not kilobytes :-)
This assumes having a DTLS PSK implementation and the associated crypto
(AES encryption, SHA-256) already present.  It also assumes a CBOR
implementation (which is needed for the actual data anyway).

Even though this was measured on a device "that ARM would like to sell
you" (was that Justin?), this should work quite well with other devices
in the RFC 7228 "Class 1" cluster".

Grüße, Carsten