Hi,
Well Acrobat can do one case i.e. able to sign a signed and encrypted pdf
document BUT can't encrypt an already signed pdf.
Steps: Create a PDF with 2 signature fields and then encrypt the pdf with
admin and user password. Now you can sign all of the empty signature fields
or if the permission to create new signature is there you can create new
signatures, without effecting the older signatures to corrupt.
PDF document state Action to Perform Can Adobe perform
the step ?
----------------------------------------------------------------------------
----------
Sign&Enc Sign
YES
Sign Enc
NO
Regards,
Wahaj
Regards,
Wahaj
"Paulo Soares" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Q1) That was discussed previously and is a limitation/feature of the PDF
> format. Even Acrobat can't do it.
>
> Q2) PdfReader.isEncrypted()
>
> ----- Original Message -----
> From: "Wahaj" <[EMAIL PROTECTED]>
> To: <[email protected]>
> Sent: Tuesday, March 22, 2005 6:27 AM
> Subject: [iText-questions] Signing & Encrypting
>
>
> Hi Guys,
>
> I have been playing with iText signing and encryption functionality for
some
> time and below are my obervations using iText-50
>
> a.. For multiple signings to work the last parameter MUST be set to true
> other wise signing again will corrupt the previous signatures.
> PdfStamper stp = PdfStamper.createSignature(reader, fout,
> '\0', new java.io.File("temp1"), true);
> a.. For Sign & Encrypting a PDF that parameter MUST be set to 'false',
> other wise an exception will come i.e.
> com.lowagie.text.DocumentException: Append mode does not support
> encryption.
> at com.lowagie.text.pdf.PdfStamper.setEncryption(PdfStamper.java:302)
> at com.lowagie.text.pdf.PdfStamper.setEncryption(PdfStamper.java:322)
>
> PdfStamper stp = PdfStamper.createSignature(reader, fout, '\0', new
> java.io.File("temp1"), false);
> a.. While signing and encrypting using the 'false' parameter as above
the
> previous signature if present gets corrupted. A more detailed result is as
> follows:
> PDF document state Action to Perform Are
Previous signatures get corrupted ?
> Sign&Enc Sign
> YES
> Sign Sign&Enc
> YES
> Enc Sign&Enc
> No
> Enc Sign
> No
> Q1) Can we do some thing to change YES to No in the above table ?
>
> Q2) Also is there an easy way to figure out whether a PDF document is
> already encrypted without catching certain exceptions ?
>
> Regards,
> Wahaj
>
>
>
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