Re: [Iot-directorate] Iotdir early review of draft-camwinget-tls-ts13-macciphersuites-06

["RFC ISE (Adrian Farrel)" <[e-mail]>]

Michael,

Very many thanks for this. It helps me a lot.

Best,
Adrian

Michael Richardson via Datatracker wrote:
> Reviewer: Michael Richardson
> Review result: Ready
>
> Reviewer: Michael Richardson
> Review result: Ready with Nits
> Document: draft-camwinget-tls-ts13-macciphersuites-06
>
> I have reviewed this document.
> I found it clear and well written.
>
> I reviewed the discussion in the TLS WG list at:
>    https://mailarchive.ietf.org/arch/msg/tls/0oy4wY4xiB1tASCBDWczh2xTVMM/
>
> I found the discussion in the TLS list as to why the TLS WG should not
> adopt
> it compelling, and I understand and agree with the reasons to go via the
> ISE.
> I do not feel that this is a run-around the WG.
>
> I did not find the three initial use cases at all compelling :-(
>   SHA256, implemented in software, is not particularly faster than AES.
>   See, for instance: https://cryptopp.com/benchmarks.html
>   where we see ~100 MiB/s {O(10^2)} for most algorithms on "big CPU"
>   (with some exceptions)
>   I suspect they are all bound by memory I/O speeds, not details of the
> algorithm.
>   I could not see an AEAD mode bench tested on that page.
>
> On smaller CPUs, the difference MIGHT be more compelling, but on the
> smaller
> such CPUs, there is usually AES acceleration, which would make use of
> an hardware acclerated AES based AEAD algorithm likely better than SHA256.
> Of course, there is probably some devices, built without any security in
> mind, which lack even that.  I question whether or not they will be able
> to
> do reasonable authentication of the TLS end points (the RSA or ECDSA
> operations).
>
> The use which I *DID* find compelling was in the fourth case, and I
> suspect
> that it covers many of the other cases.
>
>    Furthermore, requirements for providing blackbox
>    recording of the safety related network traffic can only be fulfilled
>    through using integrity only ciphers, to be able to provide the
>    safety related commands to a third party, which is responsible for
>    the analysis after an accident.
>
> I found this compelling, as it has nothing at all to do with relative
> speeds,
> or perceived latencies, but on audit trails.
>
>
>
>
>
>


-- 
Adrian Farrel (ISE),
[e-mail]