Help me with adding Digital signature through LabVIEW

[skyofprince]

Hey,

I am beginner in this section i.e. creating files. But I have understandable knowledge of LabVIEW. Can anyone help me out in adding digital signature to the specific page of the PDF? 

[rolfk]

Do you understand the PDF file format and all of its variants? While it is at its base an Encapsulated Postscript format and therefore in text, there are many variants and specialities such as compressed streams etc. that make it somehow complicated to understand and more complicated to modify without corrupting the structure.

Does your digitial signature only have to be working for your own specialiased tool (supposedly written in LabVIEW) or do you want a standard PDF reader to be able to recognize that it is a signed document and verify its consistency?

If it is only for your private tool you could probably tack on some digital signature footer to the file and make it such that the normal PDF readers will ignore it. But if it needs to be according to the official PDF digital signature standard as defined by Adobe, you most likely will not get around using an Adobe tool for instance through the command line interface. Maybe you can also install this library and invoke it through the System Exec VI. Recretating that functionality in LabVIEW is most likely an exercise in vain, not because it is inpossible but because you deal with encryption technology and no encryption is always better than badly implemented or applied encryption.

Alternatively you should be able to use iTextSharp all the way (above library makes use of some parts of it) but that is not for the faint hearted. I remember some iTextSharp based LabVIEW library had been out there, but supposedly the later versions of iTextSharp do not allow commercial use of the library without buying a license. Also I'm not sure how much of the digital signing in iTextSharp is exposed in that LabVIEW library.

[rolfk]

Do you understand the PDF file format and all of its variants? While it is at its base an Encapsulated Postscript format and therefore in text, there are many variants and specialities such as compressed streams etc. that make it somehow complicated to understand and more complicated to modify without corrupting the structure.

Does your digital signature only have to be working for your own specialiased tool (supposedly written in LabVIEW) or do you want a standard PDF reader to be able to recognize that it is a signed document and verify its consistency?

If it is only for your private tool you could probably tack on some digital signature footer to the file and make it such that the normal PDF readers will ignore it. But if it needs to be according to the official PDF digital signature standard as defined by Adobe, you most likely will not get around using an Adobe tool for instance through the command line interface. Maybe you can also install this library and invoke it through the System Exec VI. Recretating that functionality in LabVIEW is most likely an exercise in vain, not because it is inpossible but because you deal with encryption technology and no encryption is always better than badly implemented or applied encryption.

[skyofprince]

Thanks a lot for the response. I found the other solution for this i.e. by just fetching the existing digital signature and palcing it in a specfic position of the page by using iTextsharp. Now I want to add a comment or text in a specific page of an existing pdf file. 

In simple words my requirement is to edit/overwrite a pdf file. Struggling with that. 

I hope somebody has a solution.

Thanks & Regards