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I would like to include a scanned signature in my PDF and send it via email. Call me a tin-foil hat but I know how easy it is to open a PDF using, say, inkscape and extract the signature graphics from the file. I think this is a security issue and I would like to prevent my signature from being out there, floating around as a file.

Disclaimer: Of course, I'm aware that it's possible to just scan or cut out my signature anyway. I just want to increase the amount of work for someone with minor nonsense in mind. Also, I'm interested in the technical side of the problem.

Thanks!

closed as off-topic by Benedikt Bauer, T. Verron, Claudio Fiandrino, Mensch, lockstep Sep 27 '13 at 15:26

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not fall within the scope of TeX, LaTeX or related typesetting systems as defined in the help center." – Benedikt Bauer, T. Verron, Claudio Fiandrino, Mensch, lockstep
If this question can be reworded to fit the rules in the help center, please edit the question.

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    It doesn't have any relation with LaTeX, but I feel you are looking for something like Hellosign – Mario S. E. Sep 27 '13 at 11:03
  • @MarioS.E. Well yes, this would be a solution. However, as you guessed, I was looking for a TeX/LaTeX solution. – Gerome Bochmann Sep 27 '13 at 11:12
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    Maybe something like a watermark? I'm just throwing ideas – Mario S. E. Sep 27 '13 at 11:14
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    To be honest, I think you've answered your own question - the best simple solution may be to use a different signature to that which you really use (if you normally sign First Surname, try F. Surname) - it's not going to be checked against your cheques for example. Btw the last sentence wasn't just a contrived example to point out the inherent superiority in the British spelling of cheque :) – Chris H Sep 27 '13 at 11:15
  • @ChrisH Jolly good! Cup of tea then? :) – Mario S. E. Sep 27 '13 at 11:18
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Seriously, I think this is impossible, both conceptually and technically.

You already said how easy it may be to "just scan or cut your signature anyway", but that you "want to increase the amount of work for someone with minor nonsense in mind".

"Someone with minor nonsense in mind" probably is a Windows user that does not even know about inkscape or any other tool that can natively process PDF. Instead, he or shell will just open your PDF in Adobe Reader, zoom the signature to the size of the screen and do a screen dump into a bitmap file. The resolution will be good enough that nobody notices and a bitmap is less painful to use in MS Word anyway.

  • I almost expected this answer. I just remember trying to dump a bitmap from a DVD video. The result was a distorted picture. I assumed this was due to DRM and that similar technology is available for PDF. In such a case, the average troublemaker would require knowledge about how to ship around this defensive mechanism i.e. how to access the binary or memory. Nevertheless, this shows me that this is lost territory and it is more useful to apply digital signatures since my traditional signature is already floating around by the hundreds out there, just not as a file. Thanks! – Gerome Bochmann Sep 27 '13 at 13:16
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    There are DRM technologies available for PDF's, but (like all DRM) they're not going to make things difficult for the person who wants to steal your signature (as the above answer points out); they're only going to hurt the legitimate users of your PDF who can no longer open it in unsupported PDF readers (eg. Probably anything not Adobe Acrobat) – Sam Whited Sep 27 '13 at 13:28
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»I would like to prevent my signature from being out there, floating around as a file.«

Very wise. Being a lawyer in Germany, I'll never send documents and imitate my signature by putting a scan at the bottom of it. Just don't do it.


Edit: Daniel raised the question about consequences of using my own scanned signature on documents to imitate signing.

The consequence is that it is more difficult to deny to be the creator of a document carrying such a signature, if my counterpart has many documents carrying this signature and without any doubt I have fabricated those documents.

Example: I correspond with a bank and use the image of my signature: Buy shares, sell shares, sell shares short. Maybe the bank refuses to accept a plain email, but accepts a letter as PDF with my signature. After 25 of such orders I am at the mercy of the bank employees: whatever they write into a PDF, I have no way to deny being the creator of that PDF.

We could go down into details of what were prima facie evidence and so on. But as I never wish to have such a conversation, I simply don't send PDFs carrying my signature.

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    As you are a lawyer, could you elaborate a bit more on the potential consequences? I just don't get it: Anybody who has a signed document from me – electronic or paper – could easily extract and misuse my signature. Where exactly comes the difference between printing and scanning an electronic document vs scanning a paper document? – Daniel Sep 27 '13 at 12:52
  • Thanks for the Edit! – and two more questions :-) (1) Would the situation be different, if I make sure that each PDF contains an individual signature? (2) Is the situation different when sending signed documents per fax (which probably end up as PDFs on the receivers side anyway)? – Daniel Sep 27 '13 at 13:35

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