On Wed 24 Feb 2016 at 23:10:42 (+0000), Lisi Reisz wrote: > On Wednesday 24 February 2016 21:16:46 David Wright wrote: > > encrypted.pdf > > No, sadly it is not! > > Sorry, David. ;-)
Well it turns out that the problem has affected other people, eg http://superuser.com/questions/983368/both-pdftk-and-qpdf-fail-at-protecting-my-documents (still unanswered), but https://en.wikipedia.org/wiki/Portable_Document_Format#Security_and_signatures knows the answer. You have to encrypt with $ pdftk secret.pdf output /tmp/encrypted.pdf user_pw foo The man page for pdftk is therefore quite wrong when it says: Encrypt a PDF using 128-bit strength (the default), withhold all permissions (the default) pdftk 1.pdf output 1.128.pdf owner_pw foopass The owner_pw seems to be quite farcical when writing a pdf. However, if you set both passwords (with different keys), giving either key will decrypt it: $ pdftk secret.pdf output /tmp/encrypted.pdf user_pw foo owner_pw bar $ pdftk /tmp/encrypted.pdf input_pw foo cat output /tmp/u-used.pdf WARNING: The creator of the input PDF: /tmp/encrypted.pdf has set an owner password (which is not required to handle this PDF). You did not supply this password. Please respect any copyright. $ pdftk /tmp/encrypted.pdf input_pw bar cat output /tmp/o-used.pdf $ (Both /tmp/u-used.pdf and /tmp/o-used.pdf are decrypted.) One other wrinkle: xpdf seems to have problems distinguishing its options from its arguments: $ xpdf /tmp/encrypted.pdf Command Line Error: Incorrect password $ xpdf -opw bar /tmp/encrypted.pdf error: "bar" file not found $ xpdf -opw foo /tmp/encrypted.pdf error: "foo" file not found $ xpdf /tmp/encrypted.pdf -opw foo Command Line Error: Incorrect password $ xpdf /tmp/encrypted.pdf -opw bar (works) $ xpdf -upw bar /tmp/encrypted.pdf Command Line Error: Incorrect password $ xpdf -upw foo /tmp/encrypted.pdf (works) $ xpdf /tmp/encrypted.pdf -upw bar Command Line Error: Incorrect password $ xpdf /tmp/encrypted.pdf -upw foo (works) $ xpdf -upw /tmp/encrypted.pdf (maps a grey window) $ xpdf -opw /tmp/encrypted.pdf (maps a grey window) $ Mind you, though wheezy's xpdf behaves like this too, the jessie one is far more broken: most of the interactive commands and many of the options don't work anymore. Does the stretch version work any better? Cheers, David.
