PDF Digital Signatures

PDF Digital Signatures

[Andreas Schneider]

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Hello,

since  ConTeXt  supports  form  fields  in  PDFs, I wonder whether the
fields  for  digital  signatures are available as well. If not, please
consider this a feature request/wish :-)

I  received an internal document some time ago that represented a form
and  was  separated into three parts. Part one was to be filled out by
the employee (in this case: me). Under this part was a signature field
I   could   click  which  made  Adobe  Reader  prompt  for  a  digital
certificate. After I selected that, information about this certificate
appeared  inside that form field I just clicked. The other form fields
were  automatically  locked  afterwards. If I wanted to change them, I
would have to remove my signature.

Parts  two  and  three  were  similar,  but meant for management. They
needed to sign my request which in turn locked their edit fields.

So  in other words: I would like to create such forms with ConTeXt :-)
I  hate  these  work flows where people are told to "print out form x,
sign  it  and send the scanned copy via email" instead of just signing
it digitally.

It  would also come in handy for technical and business documents that
need  to be signed by the customer (for example an Interface Document,
System Design, Use Case, whatever).

I  hope  that  is  not completely out of scope for ConTeXt and not too
hard  to  implement.  Otherwise I guess I won't see that feature for a
long time.

Thanks anyway; at least for reading this :-)

-- 
Best Regards,
Andreas

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Re: PDF Digital Signatures

[Mojca Miklavec]

I'm replying off-list. I think that this might be on the list of
forbidden features (one would have to pay to adobe to be able to allow
signing document with TeX).

Mojca

On Mon, Mar 19, 2012 at 10:27, Andreas Schneider wrote:
> Hello,
>
> since  ConTeXt  supports  form  fields  in  PDFs, I wonder whether the
> fields  for  digital  signatures are available as well. If not, please
> consider this a feature request/wish :-)

I'm not sure about it, but I'm tempted to believe that digitally
signing PDFs might be one of "forbidden" functionality that requires
you to buy a licence for Acrobat. Martin Schröder usually posts this
link:
    http://en.wikipedia.org/wiki/Adobe_LiveCycle_Reader_Extensions

I have found this article, but I'm not sure if it is really legal:
    http://www.codeproject.com/Articles/14488/E-signing-PDF-documents-with-iTextSharp

Maybe we need a FAQ entry about PDF features somewhere on wiki (or at
any other place).

Mojca
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Re: PDF Digital Signatures

[Andreas Schneider]

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On Monday, March 19, 2012, at 16:41 Mojca Miklavec wrote:
> I'm replying off-list. I think that this might be on the list of
> forbidden features (one would have to pay to adobe to be able to allow
> signing document with TeX).

> Mojca

> On Mon, Mar 19, 2012 at 10:27, Andreas Schneider wrote:
>> Hello,
>>
>> since  ConTeXt  supports  form  fields  in  PDFs, I wonder whether the
>> fields  for  digital  signatures are available as well. If not, please
>> consider this a feature request/wish :-)

> I'm not sure about it, but I'm tempted to believe that digitally
> signing PDFs might be one of "forbidden" functionality that requires
> you to buy a licence for Acrobat. Martin Schröder usually posts this
> link:
>     http://en.wikipedia.org/wiki/Adobe_LiveCycle_Reader_Extensions

> I have found this article, but I'm not sure if it is really legal:
>    
> http://www.codeproject.com/Articles/14488/E-signing-PDF-documents-with-iTextSharp

> Maybe we need a FAQ entry about PDF features somewhere on wiki (or at
> any other place).

> Mojca

That's  too  bad,  although I can see Adobe's reasoning. I thought/was
hoping  that  it  was  a  simply  not-yet-implemented  feature and not
something  Adobe Acrobat and Adobe Reader specific. Well, it was worth
a shot.

Anyway for signing PDFs myself I still use and prefer JSignPDF:
http://jsignpdf.sourceforge.net/

That  is really neat and supports a lot of very helpful features (like
visible  signatures).  It's  just that it isn't a solution for general
forms  that  others should sign, since not all of them are technically
versed or willing to install some third party program. That would have
been a good use case for ready-made PDF forms with signature fields.

Thanks for your answer!

-- 
Best Regards,
Andreas

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Re: PDF Digital Signatures

[luigi scarso]

On Mon, Mar 19, 2012 at 4:41 PM, Mojca Miklavec
<mojca.miklavec.lists@gmail.com> wrote:
> I'm replying off-list. I think that this might be on the list of
> forbidden features (one would have to pay to adobe to be able to allow
> signing document with TeX).
>
> Mojca
>
> On Mon, Mar 19, 2012 at 10:27, Andreas Schneider wrote:
>> Hello,
>>
>> since  ConTeXt  supports  form  fields  in  PDFs, I wonder whether the
>> fields  for  digital  signatures are available as well. If not, please
>> consider this a feature request/wish :-)
>
> I'm not sure about it, but I'm tempted to believe that digitally
> signing PDFs might be one of "forbidden" functionality that requires
> you to buy a licence for Acrobat.
Why ? As  long it is  described in the ISO standard,  it can be
implemented in mkiv (easily is another question).
>Martin Schröder usually posts this
> link:
>    http://en.wikipedia.org/wiki/Adobe_LiveCycle_Reader_Extensions
this is about enabling features of an Adobe program. A licence is
required, but it's normal.

-- 
luigi
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Re: PDF Digital Signatures

[Kip Warner]

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On Mon, 2012-03-19 at 10:27 +0100, Andreas Schneider wrote:
>  Under this part was a signature field
> I   could   click  which  made  Adobe  Reader  prompt  for  a  digital
> certificate. 

Great idea. It would be great if one could use any OpenPGP key.

-- 
Kip Warner -- Software Engineer
OpenPGP encrypted/signed mail preferred
http://www.thevertigo.com

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Re: PDF Digital Signatures

[Mojca Miklavec]

On Mon, Mar 19, 2012 at 17:51, luigi scarso wrote:
>
>> I'm not sure about it, but I'm tempted to believe that digitally
>> signing PDFs might be one of "forbidden" functionality that requires
>> you to buy a licence for Acrobat.
> Why ? As  long it is  described in the ISO standard,  it can be
> implemented in mkiv (easily is another question).

As I said: I'm not sure whether or not it is legal to implement it or not.

There seem to be two separate issues:
(a) creating a document that others users will be able to fill in and sign
(b) signing your own document
Martin usually knows the legal issues better. I'm not sure about the
exact legal state and I'm not sure where to check it without getting
lost in "hundreds" of pages of EULA or other documents, but (b) is
described in PDF Reference Manual
(http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf)
in Chapter 12 and cannot be any more complicated to implement than all
other PDF features that Hans, Taco or Hartmut ever implemented.

Out of curiosity: is inability to create password-protected PDF files
with pdfTeX/LuaTeX due to legal issues or due to nobody caring enough
to implement it?

Mojca
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Re: PDF Digital Signatures

[Hans Hagen]

On 19-3-2012 16:41, Mojca Miklavec wrote:
> I'm replying off-list. I think that this might be on the list of
> forbidden features (one would have to pay to adobe to be able to allow
> signing document with TeX).

Is this much different from https certificates? Adobe probably runs a 
verification service.

Hans


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Re: PDF Digital Signatures

[Hans Hagen]

On 19-3-2012 22:08, Mojca Miklavec wrote:
> On Mon, Mar 19, 2012 at 17:51, luigi scarso wrote:
>>
>>> I'm not sure about it, but I'm tempted to believe that digitally
>>> signing PDFs might be one of "forbidden" functionality that requires
>>> you to buy a licence for Acrobat.
>> Why ? As  long it is  described in the ISO standard,  it can be
>> implemented in mkiv (easily is another question).
>
> As I said: I'm not sure whether or not it is legal to implement it or not.
>
> There seem to be two separate issues:
> (a) creating a document that others users will be able to fill in and sign
> (b) signing your own document
> Martin usually knows the legal issues better. I'm not sure about the
> exact legal state and I'm not sure where to check it without getting
> lost in "hundreds" of pages of EULA or other documents, but (b) is
> described in PDF Reference Manual
> (http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf)
> in Chapter 12 and cannot be any more complicated to implement than all
> other PDF features that Hans, Taco or Hartmut ever implemented.

sure, it's just that I never needed something like that

> Out of curiosity: is inability to create password-protected PDF files
> with pdfTeX/LuaTeX due to legal issues or due to nobody caring enough
> to implement it?

it's not worth the trouble. Afaik it's a second pass issue and would 
complicate the code much.

Just use qpdf to do it ... pretty fast.

Hans


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Re: PDF Digital Signatures

[Mojca Miklavec]

On Mon, Mar 19, 2012 at 23:12, Hans Hagen wrote:
> On 19-3-2012 22:08, Mojca Miklavec wrote:
>>
>> Out of curiosity: is inability to create password-protected PDF files
>> with pdfTeX/LuaTeX due to legal issues or due to nobody caring enough
>> to implement it?
>
> it's not worth the trouble. Afaik it's a second pass issue and would
> complicate the code much.
>
> Just use qpdf to do it ... pretty fast.

If qpdf exists it is probably not a legal issue to do password protection then.

But from the same perspective ... one first needs PDF to be (almost)
finished before being able to sign it. One needs to read as-good-as
the whole PDF, read the certificate from somewhere on the disk and
then sign with that certificate. If certificate is password-protected,
one also needs to provide the password somehow.

The usecase would be sending documents to officials (proving that the
document really comes from the person claiming the ownership). But it
is also true that in principle one can sign emails with PDF
attachments. It is not the same, but it comes close. Another usecase
could be, say, sending invoices to clients.


We have a company that sells crappy software for signing PDFs and XML
for over 1000 EUR per version per browser per OS (each new version for
each supported browser on a single OS costs that much; and they have a
lot of clients). And of course it never works since of course it only
supports Mac OS X 10.6 (10.7 still doesn't work), on Windows only IE 7
or Firefox 3.6 (latest Firefox won't work and it is awfully difficult
to find the old versions), on Linux probably a similar story (never
tried). And that is the only possible way to send any document to the
government. On the other hand they could just as well have used some
standard tool and it would work out of the box. So much about signing
...

Mojca
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Re: PDF Digital Signatures

[Hans Hagen]

On 20-3-2012 20:23, Mojca Miklavec wrote:
> On Mon, Mar 19, 2012 at 23:12, Hans Hagen wrote:
>> On 19-3-2012 22:08, Mojca Miklavec wrote:
>>>
>>> Out of curiosity: is inability to create password-protected PDF files
>>> with pdfTeX/LuaTeX due to legal issues or due to nobody caring enough
>>> to implement it?
>>
>> it's not worth the trouble. Afaik it's a second pass issue and would
>> complicate the code much.
>>
>> Just use qpdf to do it ... pretty fast.
>
> If qpdf exists it is probably not a legal issue to do password protection then.

Why?

Hans

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Re: PDF Digital Signatures

[Michael Hallgren]

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Le mardi 20 mars 2012 à 20:23 +0100, Mojca Miklavec a écrit :
> On Mon, Mar 19, 2012 at 23:12, Hans Hagen wrote:
> > On 19-3-2012 22:08, Mojca Miklavec wrote:
> >>
> >> Out of curiosity: is inability to create password-protected PDF files
> >> with pdfTeX/LuaTeX due to legal issues or due to nobody caring enough
> >> to implement it?
> >
> > it's not worth the trouble. Afaik it's a second pass issue and would
> > complicate the code much.
> >
> > Just use qpdf to do it ... pretty fast.
> 
> If qpdf exists it is probably not a legal issue to do password protection then.

You mean strong encryption? Some countries, regimes I should rather say,
are not in favour of such... Sad fact, IMHO.

Signing a document digitally, should never be much of an issue, in your
mentioned legal context, though. Well, needs to be honoured by the
receiving party... but... hey, make regimes modern ! :)

Cheers,
mh

> 
> But from the same perspective ... one first needs PDF to be (almost)
> finished before being able to sign it. One needs to read as-good-as
> the whole PDF, read the certificate from somewhere on the disk and
> then sign with that certificate. If certificate is password-protected,
> one also needs to provide the password somehow.
> 
> The usecase would be sending documents to officials (proving that the
> document really comes from the person claiming the ownership). But it
> is also true that in principle one can sign emails with PDF
> attachments. It is not the same, but it comes close. Another usecase
> could be, say, sending invoices to clients.
> 
> 
> We have a company that sells crappy software for signing PDFs and XML
> for over 1000 EUR per version per browser per OS (each new version for
> each supported browser on a single OS costs that much; and they have a
> lot of clients). And of course it never works since of course it only
> supports Mac OS X 10.6 (10.7 still doesn't work), on Windows only IE 7
> or Firefox 3.6 (latest Firefox won't work and it is awfully difficult
> to find the old versions), on Linux probably a similar story (never
> tried). And that is the only possible way to send any document to the
> government. On the other hand they could just as well have used some
> standard tool and it would work out of the box. So much about signing
> ...
> 
> Mojca
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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> ___________________________________________________________________________________


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Re: PDF Digital Signatures

[Martin Schröder]

2012/3/20 Mojca Miklavec <mojca.miklavec.lists@gmail.com>:
> If qpdf exists it is probably not a legal issue to do password protection then.

Of course.

> But from the same perspective ... one first needs PDF to be (almost)
> finished before being able to sign it. One needs to read as-good-as
> the whole PDF, read the certificate from somewhere on the disk and
> then sign with that certificate. If certificate is password-protected,
> one also needs to provide the password somehow.

You can technically sign only parts (IIRC streams) of a PDF.

> government. On the other hand they could just as well have used some
> standard tool and it would work out of the box. So much about signing
> ...

gpg is free. So is jpdfsign.
See also http://wiki.cacert.org/PdfSigning

Best
   Martin
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