> On 2023-07-03, Bram Moolenaar <b...@moolenaar.net> wrote:
> > I suppose encrypting the file won't be possible, since the reader does
> > not know how to decrypt it. Or does the Preview app support encryption
> > somehow?
>
> Yes, macOS's Preview supports (at least some?) encrypted PDFs. I did
> a quick test by encrypting a random PDF document with qpdf:
>
> qpdf --encrypt PASSWORD OWNERPASSWORD 256 -- in.pdf out.pdf
>
> and by opening out.pdf with Preview, which prompted for a password
> before opening the document.
I could find help with:
% qpdf --help=encryption
Create encrypted files. Usage:
--encrypt user-password owner-password key-length [options] --
Either or both of user-password and owner-password may be empty
strings. key-length may be 40, 128, or 256. Encryption options are
terminated by "--" by itself.
I don't like passing the password on the command line, but I suppose
there is no other way.
There is no explanation of "user-password" and "owner-password", other
than that they may be empty. Is there a recommended usage?
> > The alternative is to not use a temp file but write the text through a
> > pipe/socket. That also avoids the need to find the right moment to
> > delete the temp file. Can we do this somehow?
>
> With Preview? I don't think so. But if one wants to get fancy, the PDF
> can be written to the system clipboard and then Preview can be asked to
> create a new document from the clipboard's content (using AppleScript).
> Then, the clipboard content can be erased.
The big question is: is this safe? Is it impossible for someone else to
get the text in not encrypted form?
> Or, even better, one could create a (sufficiently large) RAM disk with
> something like:
>
> hdiutil attach -nomount ram://204800
> diskutil erasevolume APFS TempDisk /dev/diskN
>
> use it as volatile storage, then destroy it:
>
> diskutil eject /Volumes/TempDisk
>
> The RAM disk can likely be formatted with an encrypted file system, too.
OK, so there are options. Which one should we use? I can guess that
"ram://" specifies using a RAM disk. What is the "204800" for?
--
If it's sent by ship then it's cargo.
If it's sent by road then it's a shipment.
Dave Allen
/// Bram Moolenaar -- b...@moolenaar.net -- http://www.Moolenaar.net \\\
/// \\\
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