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Subject: Re: [dss-x] Initial draft of the Visual Signature profile
Dear all, Ezer Farhi wrote: > Hello Leonard, > > Follows some my comments on your raised issues: > - The digital signature value is indeed not applicable to PDF, I'm not sure this is true ... the only English resource I have on this is the following and I'm not sure it's publicly available ... cf. http://ieeexplore.ieee.org/iel5/10823/34117/01625379.pdf#page=5 : > The visualization of the signature value can be realized by > excluding two areas within the PDF document from the > calculation of the hash value. On the one hand, this would be > the attribute ”Contents” and on the other hand a second area > with the same content as defined in the ”Contents” attribute, > representing the visualization of the signature value. Both > sections are excluded from the signature by setting the attribute > ”ByteRange” appropriately. This method conforms to the PDFSpecification, > which allows the exclusion of certain areas via > the ”ByteRange” attribute. However, in the course of a concrete > realization, there could be some problems because Adobe > Acrobat/Reader allow only two entries in the attribute ”Byte > Range” (= One exclusion). An individual signature handler is > needed for validating the signature and both exclusions. Ezer Farhi wrote: > but may > be applicable to other document formats such as the one that is used in > the Austrian Federal Chancellery. > Some Resources on this, unfortunately in German ... I'll translate the relevant sections as soon as I have identified, which they are ... Projektseite auf EGovLabs http://egovlabs.gv.at/projects/pdf-as/ Spezifikation der PDF-Amtssignatur http://egovlabs.gv.at/docman/view.php/8/26/PDF-AS-Spezifikation-2.0.0.pdf Projektseite auf Demo-EGIZ http://demo.egiz.gv.at/plain/projekte/signatur_im_e_government/pdf_signatur Spezifikation der PDF-Amtssignatur http://demo.egiz.gv.at/plain/content/download/527/3056/file/PDF-AS-Spezifikation-2.0.0.pdf kind regards Konrad
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