IFX Mail Archive: RE: IFX> Sender URI Stamp

IFX Mail Archive: RE: IFX> Sender URI Stamp

RE: IFX> Sender URI Stamp

From: Rick Seeler (rseeler@adobe.com)
Date: Mon Feb 03 2003 - 16:59:50 EST

  • Next message: Gail Songer: "RE: IFX> Sender URI Stamp"

    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. Hmmmm.

    -----Original Message-----
    From: owner-ifx@pwg.org [mailto:owner-ifx@pwg.org] On Behalf Of Gail Songer
    Sent: Monday, February 03, 2003 1:14 PM
    To: Rick Seeler
    Cc: ifx@pwg.org
    Subject: RE: IFX> Sender URI Stamp
    Importance: High



    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?





    -----Original Message-----
    From: Rick Seeler [mailto:rseeler@adobe.com]
    Sent: Monday, February 03, 2003 12:50 PM
    To: Gail Songer
    Cc: ifx@pwg.org
    Subject: RE: IFX> Sender 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 signed.


    Is this what you were looking for?




    -----Original Message-----
    From: owner-ifx@pwg.org [mailto:owner-ifx@pwg.org] On Behalf Of Gail Songer
    Sent: Monday, February 03, 2003 12:11 PM
    To: ifx@pwg.org
    Subject: IFX> Sender URI Stamp



    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


    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?



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