Re: [Suit] Wording for integrated payload size

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 17 December 2019 19:38 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Brendan Moran <Brendan.Moran@arm.com>
cc: Dave Thaler <dthaler@microsoft.com>, suit <suit@ietf.org>
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Date: Tue, 17 Dec 2019 14:38:02 -0500
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Subject: Re: [Suit] Wording for integrated payload size
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Brendan Moran <Brendan.Moran@arm.com> wrote:
    > I see why the use of RAM as a requirement is surprising. There are two
    > requirements here. I believe that one of them is required and one is
    > optional.

    > It is required that the manifest be held invariant between verification and
    > processing. This could mean storing in internal RAM or NVRAM, storing in a
    > secure external memory, etc.

I think that you are also attempting to defend against hardware attacks where
the contents of memory get changed mid-process.  That's not *explicitely*
stated in the text.

But, it's why you speak about internal RAM (vs RAM), and I guess "secure
external memory" means that it has some cryptographic checks not attackable
From outside the SoC.

Maybe the attempt to abstract the text is detracting from understanding?

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-