Peter:
... all credit to the authors for bring all the discussion to
the point of concrete specification.
I agree. Based on your comments, we both agree that the I-D should
describe the security services that are provided by each MIME-PEM content
type. I think that the I-D should also describe the security services that
are provided by the possible combinations. In my opinion, few users will
care about the services offered by signed ciphertext.
(I know Russ, you don't think much of trusted agent security
designs. But, MOA signatures computed by the MTA switch (without
complex crypto, albeit), over potentially-encrypted content are
actually being used between commercial VANs to perform charging
and settlement. Of course this has nothing to do with the VAN
users. Not does it have much to do with privacy or confidentiality.
but there is more to commercial provider-based message switching
than just the users.)
Peter, I understand this scenario, but I think that MIME-PEM would not be
well suited to this task. The VAN operator would rather have a mechanism
that signed the whole content. RFC1421 PEM is better suited to this task
because it always protects the whole content.
Russ