Subject: Re: [Dtls-iot] WGLC for DTLS Profile draft: 11/11/2014 - 11/25/2014

From: John Mattsson <[email-masked]>
Date: Wed, 19 Nov 2014 15:07:54 +0000

Hi,

Agreeing with Hannes on HTTP/2 for IoT.

While AES-CCM is better for small devices, AES-GCM is faster on large
devices. See for example (https://eprint.iacr.org/2014/186.pdf, Table 4,
“single message”). I also think it would be a bad idea for HTTP/2 to
require implementation of a cipher suite with only a 8 byte authentication
tag. The IoT devices that implements HTTP/2 can probably take the cost of
implementing GCM as well.

Concerning UTA BCP, I think Roberts suggestion “I think UTA should state
the use of approved AEAD ciphers as BCP” makes sense.

Another aspect is that we will probably soon have ChaCha20-Poly1305 as a
new AEAD cipher: 
https://tools.ietf.org/html/draft-irtf-cfrg-chacha20-poly1305-03

I suspect this to be popular for IoT devices without HW support for AES,
and it strengthens the case for UTA BCP to not recommend just GCM but all
approved AEAD ciphers.

Cheers,
John