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Posted to fop-dev@xmlgraphics.apache.org by Miguel A Paraz <mp...@mparaz.com> on 2002/07/20 16:55:55 UTC
Need advice in implementing signed PDF files
Hi,
I've been reading the code and I hope to get some tips.
On Wed, Jul 17, 2002 at 02:58:13PM +0200, Keiron Liddle wrote:
> If I understand it properly you would need to add an Encrypt pdf object
> that is referenced in the documents trailer dictionary.
That is, write out the signature with PDFDocument.outputTrailer?
Or, add it to trailerObjects using addTrailerObject?
> The you would need to encrypt all pdf streams using the appropriate
> algorithm. If JCE can handle this then it would be used to encrypt the
> stream.
Thus I will subclass PDFFilter.
>From my reading of the code, the scope of the PDFFilter is only inside
the PDFStream, and the document is composed of multiple PDFStreams.
If I am correct, then the signing process has to be closer to the output
level. For instance, using a FilterOutputStream to peek at the data being
written out at the PDFRenderer level. Or, I could use a single
java.security.Signature instance for all the PDFFilter subclass instances.
If I am wrong, and I can use a PDFFilter subclass, how can I extract my
java.security.Signature instance from the PDFFilter, to write it out
(java.security.Signature.sign())? The filters in PDFStream are not
referenced by name.
> - organise the configuration for password etc.
If a PDFFilter subclass is to be used, how can this have access to the
configuration file?
Thanks in advance!
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Re: Need advice in implementing signed PDF files
Posted by Keiron Liddle <ke...@aftexsw.com>.
On Mon, 2002-07-22 at 19:12, Miguel A Paraz wrote:
> > I don't know. What do you think it should do?
>
> Sorry, let me rephrase that. My question is, what is the proper way for
> a PDFFilter subclass to read values from the configuration file?
> The signing system would need access to the name of the private key, for
> instance.
Are we talking maintanence branch, if so the configuration is static and
you simply put a key+value pair in the config and read the value using
the key.
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Re: Need advice in implementing signed PDF files
Posted by Miguel A Paraz <mp...@mparaz.com>.
On Mon, Jul 22, 2002 at 11:51:05AM +0200, Keiron Liddle wrote:
> As I misunderstood the original question it appears there is a slight
> difference to what needs to be done.
> What exactly does it need to do to sign a pdf file. Does it need to read
> all data in all streams and then create a single signature number. If so
> then it sounds like there needs to be some adjustment to how the filters
> are created and used in order to accomodate what you want.
I read the spec. It turns out that signatures are part of Acrobat Forms
(chapter 6.14). It's not clear to me, what in particular is being signed -
the rest of the form, perhaps?
I am going to find out.
> > If a PDFFilter subclass is to be used, how can this have access to the
> > configuration file?
>
> I don't know. What do you think it should do?
Sorry, let me rephrase that. My question is, what is the proper way for
a PDFFilter subclass to read values from the configuration file?
The signing system would need access to the name of the private key, for
instance.
--
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+63-916-423-7922
---------------------------------------------------------------------
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Re: Need advice in implementing signed PDF files
Posted by Keiron Liddle <ke...@aftexsw.com>.
On Sat, 2002-07-20 at 16:55, Miguel A Paraz wrote:
> Hi,
> I've been reading the code and I hope to get some tips.
>
> On Wed, Jul 17, 2002 at 02:58:13PM +0200, Keiron Liddle wrote:
> > If I understand it properly you would need to add an Encrypt pdf object
> > that is referenced in the documents trailer dictionary.
>
> That is, write out the signature with PDFDocument.outputTrailer?
> Or, add it to trailerObjects using addTrailerObject?
Add a new object to the pdf file that is referenced in the trailer
dictionary using the pdf object reference.
> > The you would need to encrypt all pdf streams using the appropriate
> > algorithm. If JCE can handle this then it would be used to encrypt the
> > stream.
>
> Thus I will subclass PDFFilter.
>
> >From my reading of the code, the scope of the PDFFilter is only inside
> the PDFStream, and the document is composed of multiple PDFStreams.
>
> If I am correct, then the signing process has to be closer to the output
> level. For instance, using a FilterOutputStream to peek at the data being
> written out at the PDFRenderer level. Or, I could use a single
> java.security.Signature instance for all the PDFFilter subclass instances.
>
> If I am wrong, and I can use a PDFFilter subclass, how can I extract my
> java.security.Signature instance from the PDFFilter, to write it out
> (java.security.Signature.sign())? The filters in PDFStream are not
> referenced by name.
As I misunderstood the original question it appears there is a slight
difference to what needs to be done.
What exactly does it need to do to sign a pdf file. Does it need to read
all data in all streams and then create a single signature number. If so
then it sounds like there needs to be some adjustment to how the filters
are created and used in order to accomodate what you want.
> > - organise the configuration for password etc.
>
> If a PDFFilter subclass is to be used, how can this have access to the
> configuration file?
I don't know. What do you think it should do?
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