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From RJC 2009 <rjc2...@gmail.com>
Subject Re: Need help to protect PDF with owner password
Date Wed, 22 May 2019 01:28:36 GMT
Thanks Tilman Hausherr and Marc Kaufman for your time & help.

I came across following post at iText tech support faq talking about
similar topic.
https://itextpdf.com/en/resources/faq/technical-support/itext-7/how-decrypt-pdf-document-owner-password

Seems the following pdf file which they have shared is encrypted and does
not allow to overwrite the owner password using PDFBox (2.0.15).
http://gitlab.itextsupport.com/itext/sandbox/raw/master/resources/pdfs/hello_encrypted2.pdf

I'm just wondering how does this works and are there any similar
implementation in PDFBox.

On Wed, May 22, 2019 at 7:45 AM Marc Kaufman <marc@eeph.com> wrote:

> Which is, of course, a violation of the "agreement" between PDF and
> Readers (ignored by everyone, it seems, except Adobe). In
> Acrobat/Reader, you need to open with the Owner password in order to
> change permissions. Opening with the User password should honor
> permissions and not allow changing of permissions.
>
> Marc
>
> On 5/21/2019 9:42 AM, Tilman Hausherr wrote:
> > Am 17.05.2019 um 09:47 schrieb RJC 2009:
> >> Here is my test program which is trying to disable the printing
> >> option and
> >> protect the document with an owner password.
> >>
> >> However, if I use the resultant PDF and run the program again with a
> >> DIFFERENT owner password then it ENABLE the printing option.
> >>
> >>
> >>
> >> Basically I need to disable the printing option in PDF with an owner
> >> password and the printing option cannot be enabled back without using
> >> the
> >> original owner password.
> >
> >
> > I should have read the text more carefully (and continue reading after
> > "2.0.5"). This is by design. When you open with the user password then
> > the file is decrypted and can be manipulated, reencrypted, everything.
> > The owner password is just an extra so that a software can decide that
> > you're the owner. That is why there are so many tools on the internet
> > that allow to change the permissions of PDF files.
> >
> > Read also this:
> >
> > https://www.cs.cmu.edu/~dst/Adobe/Gallery/anon21jul01-pdf-encryption.txt
> >
> >
> > Tilman
> >
> >
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