[NTG-context] PDF Signature Fields

Hans Hagen pragma at wxs.nl
Thu Mar 10 16:56:03 CET 2016


On 3/10/2016 11:04 AM, Andreas Schneider wrote:
> Hello Hans,
>
> after comparing eforms and the result of a document edited by Acrobat,
> the relevant portions in the spec (PDF 32000-1:2008) are:
> Section 12.7.4.5, with tables 232 and 233.
>
>  From what I see it should be possible to add a field /FT /Sig with and
> without a /Lock dictionary.
> The /Lock dictionary created by Acrobat also specifies the optional
> /Type /SigFieldLock (eforms doesn't, but when in doubt, I trust Adobe
> more than eforms ;-))
>
> Here is an example from the PDF stream of a document manually forged
> with Acrobat:
> %% Object stream: object 167, index 37; original object ID: 475
> <<
>    /AP <<
>      /N 188 0 R
>    >>
>    /DA (/Helv 0 Tf 0 g)
>    /F 4
>    /FT /Sig
>    /Lock 187 0 R
>    /MK <<
>    >>
>    /P 196 0 R
>    /Rect [
>      253.965
>      163.306
>      525.056
>      186.143
>    ]
>    /Subtype /Widget
>    /T (Gehnehmiger Unterschrift)
>    /Type /Annot
>>>
> %% Object stream: object 187, index 57; original object ID: 495
> <<
>    /Action /Exclude
>    /Fields [
>      (Einrichter Name)
>      (Einrichters Unterschrift)
>    ]
>    /Type /SigFieldLock
>>>
>
> ("Einrichter Name" is another Text Field --> /FT /Tx [...] /Subtype
> /Widget [...] /T (Einrichter Name)
>   "Einrichters Unterschrift" is another Signature Field)

next beta:

\setupinteraction[state=start]

\starttext

     \definefield[x][signature]

     \field[x]

\stoptext



> Am 2016-03-09 16:16, schrieb Hans Hagen:
>> On 3/9/2016 2:11 PM, Andreas Schneider wrote:
>>> Hello all,
>>>
>>> is there currently any mechanism in ConTeXt similar to the LaTeX digsig
>>> or eforms package?
>>> I want to add a form field that can be digitally signed (which is now
>>> already possible with Acrobat Reader, not just with Acrobat Pro).
>>>
>>> Additionally (like the mentioned eforms package) it would be nice, if
>>> you could specify other form fields that should be locked once the
>>> signature field is actually signed (according to the PDF spec this is
>>> simply set via a dictionary).
>>
>> it's probably something trivial to implement so what are the relevant
>> fields (paragraphs/tables/dics/fields in the pdf spec) .. i'm not
>> going to reverse engineer some package but start from the spec
>>
>>> Anyway: can this currently be achieved with ConTeXt? If not: is there
>>> any chance to get that feature added sometime? :-)
>>
>> so far i never bothered with anything signature (i must say that i
>> never ran into such docs and it would not make them more valid to me
>> anyway)
>>
>> Hans
>>
>> -----------------------------------------------------------------
>>                                           Hans Hagen | PRAGMA ADE
>>               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>>       tel: 038 477 53 69 | www.pragma-ade.com | www.pragma-pod.nl
>> -----------------------------------------------------------------
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-- 

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
       tel: 038 477 53 69 | www.pragma-ade.com | www.pragma-pod.nl
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