Re: [Gen-art] [Last-Call] Genart last call review of draft-ietf-rats-architecture-21

[Laurence Lundblade <[e-mail]>]

Below

> On Aug 20, 2022, at 1:38 PM, Michael Richardson <[e-mail]> wrote:
> 
> Gyan Mishra via Datatracker <[e-mail] <mailto:[e-mail]>> wrote:
> 
>> Section 3 describes the environment of an attester.  Section
>> 3.2 clearly describes a layered environment, however section 3.3
>> describes a composite environment using a carrier grade router as an
>> example.  I think here the composite should be described just as is
>> done in the layer environment section but not referencing an
>> environment use case that may not be applicable to RAT.
> 
> I guess I don't really follow what you are suggesting here.
> 
>> So within a
>> carrier grade router chassis the backplane communication is all done
>> vendor proprietary no external elements so I don’t see how trust comes
>> into play as well as the backplane communication is hardware bus
>> elements for backplane throughput for the LC and then as well router OS
>> software component for the backplane communication. I think maybe
>> choosing a better example that applies to RAT composite environment
>> would be better.
> 
> Yes, the way in which the Evidence is relayed is vendor proprietary, but the
> the Evidence and/or Attestation Results are then relayed to an external verifier.

I don’t know anything about router architecture, but do about mobile phone architecture which I consider a candidate for composite attestation.

A mobile phone based on a chip like a Qualcomm Snapdragon has many subsystems. Something like this:
- A TEE and/or HW root of trust, perhaps controlled by the chip vendor, not the phone vendor
- A Secure Element for payments or eSIM
- A SIM card 
- The general purpose CPU running Android and is controlled by the phone vendor
- A video playback subsystem that does content protection and is isolated from the main CPU
- A cellular modem
- A Bluetooth subsystem isolated from the modem
- …

There are several tiers of security and multiple vendors.

LL