Should qpdfview open 256-bit encrypted file?

Asked by anonymous pickle

 I use qpdf to encrypt a pdf file with a 256 bit key:
qpdf --encrypt pwd pwd 256 -- in.pdf out.pdf
When out.pdf is opened with qpdfview, it requests the password, then fails, reporting "Could not open out.pdf" (gui) or "Error: Incorrect password" (command line). out.pdf can be opened in firefox.

Files encrypted with 128 or 40 bit key are opened with no problem. Should qpdfview be able to open files with 256 bit encryption? Thanks.

MX Linux 18.3_x64
kernel 4.19.0-6-amd64
qpdfview 0.4.18
PDF support using Poppler 0.48.0
PS support using libspectre 0.2.8
DjVu support using DjVuLibre 3.5.27
Printing support using CUPS 2.2.1

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Adam Reichold
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Best Adam Reichold (adamreichold) said :

Hello pickle,

it depends on your Poppler version. You can check whether "pdfinfo -opw pwd out.pdf" works on the command line to verify whether the Poppler library installed on your system works or not. Using Poppler 21.05.0, it does seem to work both using "pdfinfo" as well "qpdfview".


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anonymous pickle (elnecio) said :

The pdfinfo command reports "incorrect password" I guess for some reason MXLinux includes poppler libraries that can't handle 256 bit encryption. I have reported this to MXLinux developers.

Thanks for your reply.

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anonymous pickle (elnecio) said :

Thanks Adam Reichold, that solved my question.