[Sframe] John Scudder's No Objection on draft-ietf-sframe-enc-07: (with COMMENT)

[John Scudder via Datatracker <[e-mail]>]

John Scudder has entered the following ballot position for
draft-ietf-sframe-enc-07: No Objection

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COMMENT:
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Thanks for this document. To the extent I’m qualified to review it, I found it
clear, comprehensive, and readable. I have a minor comment and a trivial
question.

Comment:

“Invalid ciphertexts SHOULD be discarded in a way that is indistinguishable (to
an external observer) from having processed a valid ciphertext.”

This might be clear to someone within your ecosystem, but I wonder what exactly
is meant by “external” here. I infer it means an observer without any access to
a system that’s participating in the conference, because otherwise, I don’t see
how this requirement could be met (consider the case where the discarded
ciphertext is a keyframe, for example).

Whether this calls for clarification or not is up to you.

Question:

I also wonder as to the practical value of the compressed CTR representation —
I would have imagined that most use cases would emit more than 8 plaintexts,
and for that matter, if there are 8 or fewer plaintexts to be emitted over the
lifetime of the KID, the application is so low-volume that maybe the
optimization doesn’t buy you much as compared to, say, adding another bit to
the compressed KID field.

But this is just idle curiosity, even if the answer was “yeah, it’s not that
useful” I wouldn’t advocate changing the encoding at this late date.