Subject: SCVP responses containing only {path, rev-info}

From: "Michael Myers" <[email-masked]>
Date: Fri, 9 Jul 2004 13:40:01 -0700

All,

Apologies in advance for the awkward subject line but the SCVP
I-D provides no explicit means to say "DPD".  Nonetheless, for
the purposes of this note, interpret "DPD" as a macro for "SCVP
responses containing ONLY {path, rev-info}".

You may recall some time ago discussions on whether or not DPD
should be signed.  It was concluded that because the data
objects contained in such a response are themselves signed, the
security assurances afforded by overlaying an additional
signature were of such a degree that the risks are a matter of
local policy--providing that the document defined a means to
enable activation of DPD signing.

Since the development of that rough consensus, several off-list
discussions have been conducted with a view towards the precise
definition of those means.  The most recently proposed mechanism
appears to enable a consensus that will close this issue.  With
additional apologies in advance to all participants in the
off-list discussions, I believe it is time to bring this issue
to the WG.

The proposed mechanism is as follows.  Assume there exists a new
SCVP request flag governing the production of DPD signatures.
Then:

(1) If the client indicates DPD signatures are not required,
    the server MAY return an unsigned response, a signed
    response, or an error.

(2) If the new request flag is not present, the server MUST
    return a signed response or an error.

(3) Unless the client indicates signatures are not required,
    the client MUST verify the signature on the response.

I would prefer to invert the sense of #2 since by RFC 3379's
definition DPD is to a first degree just a proxy for the diverse
protocols and schemas currently used to access PKI information.
Where the previously hypothesized replay attacks become reality,
turn on the flag.  But maybe that is just me.

I think it is time others were given the opportunity to voice
their opinions.

Thoughts, anyone?

Mike

---

From: David Engberg <[email-masked]>
Date: Fri, 09 Jul 2004 17:26:18 -0400

I support this proposal.

I do agree with Mike, and would also prefer to invert #2 (DPD may be 
unsigned unless client explicitly requests a signature), but I would 
ultimately be fine with either form.

Thanks

Michael Myers wrote:
> ...