Right now it's spec'ed that the Stamp must be part of the image, and
appear in one of three places, as a cover sheet, top of the first page
or top of every page.
I like the idea of the shared image for all of the pages.
Yes, I understand that the 'Document Information Dictionary' alone is
not enough, also having the information in the image should be required.
I just wasn't sure where you were going with this.
As for you question; "maybe": depending on what the digital signature
is used for. If I generated a digitally signatured PDF/is doc on my
system and placed it on a web site, then someone transmitted that
document using IPPFAX to someone else, my original signature should not
be used as a "Fax transmission header". This is an interesting
situation. Do we want to limit DSigs to just being used for
"transmission headers": I think not. Therefore, we can either have two
uses for them, or find another way to handle the "transmission header".
We could change the PDF/is spec to allow for more than one DSig (it is
allowed in PDF) very easily (one sentence in section 3.3.16). We would
then have to specify that a certain DSig is for "transmission header"
and all others are for "other purposes". Each PDF/is document would
only be able to have one of these "transmission header" DSigs. We could
specify this using the DSig's 'Name' or 'Reason' fields having a special
value for the "transmission header". Of course, using DSigs this way
would move DSig support for the Consumer and Producer from 'Optional' to
'Required'. Do we want this? Using DSigs in this way, I believe, is a
superior way to tag a fax transmission to adding some image of the
information in the header of each page; but it has a cost. One other
benefit of this -- once the document is received, it can be printed out
without the header tag information in the printout, if desired.
If we do not want to use DSigs this way, we are back to using an image
of the header (are there other options?). We could specify that this
image header as part of the spec. We could specify it as a shared image
for all pages of the document. This would allow the recipient to print
the document without the header, if so desired. But, by doing this, we
make it easier for someone to replace the header during transmission.
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Gail
Sent: Monday, February 03, 2003 1:14 PM
To: Rick Seeler
Subject: RE: IFX> Sender URI Stamp
On a fax document, the date/time and ID of the sending machine are part
of the transmitted image; added to the image by the sender.
In keeping with current fax, I would think that we still want this
information as part of the image. So I guess I think that answer is "no,
the information in the dictionary is not quite enough". If the doc is
printed and the soft copy discarded then this information is lost.
The digital signature does validate the data from the originating
sender, but what if the receiving user decides to try to re-fax what he
just got? Do we replace the signature and the URI stamp?
A digital Signature gives you a tamper-proof way to time-stamp a
document, but besides that...
What about using the information in the "Document Information
Dictionary" (See Table 9.2 in the PDF Reference 1.4)? This dictionary
is already part of the PDF/is spec. and should be all that is needed.
Of course, it's not tamper proof unless the document is also digitally
Is this what you were looking for?
It's occurred to me that with PDF we have level of portability that we
didn't have before. However the IFX spec requires that the sender add
the URI of the sender:
The Sender MUST place the Sender's URI, i.e., the value of the
"sender-uri" attribute (see section 8.3), along with the date
and time, in one of the following places, DEPENDING ON
1. On a cover page automatically generated by the Sender that is sent
before the rest of the document.
2. Merged with the first page of the document.
3. At the top of every page of the sent Document.
The Sender MAY include additional data (Sending User, Receiver
identity, etc.). As for regular FAX, it is RECOMMENDED that
this information be represented as bit map data, so that it is
more difficult for it to be modified before it gets to the
My first thought was to add an optional field to the PDF that indicated
where the Stamp was located. If the doc was resent, then the second
sender could replace the Stamp with its own stamp. But if the doc was
digitally signed then either the Signature would be lost or invalidated.
Anything thoughts on how we should handle this?
This archive was generated by hypermail 2b29 : Mon Feb 03 2003 - 17:46:44 EST