[Poppler-bugs] [Bug 99416] Sign PDF with digital signature

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99416

--- Comment #53 from Albert Astals Cid <aacid at kde.org> ---
(In reply to Hans-Ulrich Jüttner from comment #50)
> (In reply to Adrian Johnson from comment #49)
> > (In reply to Hans-Ulrich Jüttner from comment #48)
> > > I think that re-reading a document which just has been written with poppler
> > > and writing it again whithout changes should produce an identical document.
> > 
> > Should does not mean it always will. It introduces a constraint on poppler
> > that prevents any future changes that alter that assumption.
> > 
> > I still have not seen a good explanation for why the you think the signing
> > should work this way.
> 
> We simply have different ideas about the in memory representation of a PDF
> file.
> In my opinion the bytes on disk should be reproducible from the in memory
> representation whenever possible. Especially when dealing with signatures
> this is desirably. If some time in the future one wants to support multiple
> signatures on PDF documents with the second signature after the ByteRange
> of the first one, then the first signature should not be invalidated by
> writing the document with the second signature.
> 
> In your opinion the bytes on disk need not be reproducible from the in memory
> representation.

Let's not delve into philosophical questions and let's try to finish this
patch, we're already at comment #53

> 
> > 
> > > But with the multiple spaces in the ByteRange on disk this would not be the
> > > case. Moreover, multiple spaces separating objects in PFD files are not
> > > allowed by more restrictive standards like PDF/A.
> > 
> > Then we can use '0's. But in any case we don't support PDF/A.
> 
> Leading '0's on the numbers in ByteRange would be even worse. These numbers
> then probably would be mistakenly read as 0 by at least some PDF software.

That'd be stupid, why would anyone parse 000004 as anything different than 4?
I'm almost even sure the specification mentions leading 0 have to be ignored.

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