problems with encrypted PDFs

Next problem with this pdf: print the same file but now with following options:

- PDF Spec: conform to 1.6
- use PDF security
- no owner and no user password
- 40 bit encryption

This file can also be opened fine with Acrobat Reader but always says 0 pages with QuickPDF. This is caused be the fact that quickPDF cannot create the page dictionary. When you look at the PDF source you can see that the page object is not available as a plain object but contained in an object stream (which is encrypted according to the settings).
So what happens when the file is loaded: TPDFDocument.ValidPDFSource reads Header and Trailer and then tries to build the pagetree. And here it fails as it cannot read the content. Internaly it had to read the page object from the object stream (which it tries to do right). But it cannot decode the stream as it seems always comes back with a data error. Here the reason is that the stream is still encrypted! During reading the page it looks if it has to unencrypt the stream. And as the internal password is blank ('') it doesn't encrypt. So why is it ''? If you look at TPDFDocument.SetPassword you can see that a call to SetPassword with a valid password (alos the blank one) doesn't leave the internal password blank but set it at least to '!'.
And this is the solution: set the internal password to '!' before building the pages dictionary.

function TPDFDocument.ValidPDFSource: Boolean;
var
LinData: string;
OP: Integer;
LinObj: string;
LinGen: string;
LinIO: TPDFIndObj;
LinDict: TPDFDictionary;
TestObj: TPDFObject;
begin
...
      Result := True;
      if Assigned(FPageTree) then FPageTree.Free;

      // UKO 09.11.2006
      // Password needs to be set here to ensure that encrypted Object streams
      // containing page objects can be decrypted properly.
      Password := '';

      FPageTree := TPDFPageTree.Create(GetPagesDict, FImages);

btw: LoadFromStream also set the password to '' (-> internal password to '!'), but only after loading the PDF source which is to late for encrypted object streams.

in general: Current QuickPDf will fail to load a PDF whenever it contained page objects in an object stream and the PDF is encrypted. The above source change should
fix this.


HTH,
Uli

Has this issue with UNENCRYPT been addressed in the latest release? Thanks for your support.

I fear it's not included: I just have looked on the source (5.21) and only the second change is included as a comment. Maybe Marian has found another solution so that my original code is obsolete.

Ulrich

I am having a problem with decryption as well, though I don't know if it's the same problem or different.

My encryption is performed by QuickPDF, at 128bits, with both an owner and user password. When the saved file is opened in Acrobat Reader (6.0), it accepts both passwords and properly handles the document, along with the permissions I set from within QuickPDF.... so it appears there is no problem with encryption.

When I decrypt from within QuickPDF I don't get an error back -- the return value is proper according to owner or user password as provided. There are two glaring problems that I can see though. My document consists of a background image, and 68 form fields.

When decrypted by QuickPDF, it still agrees that there are 68 form fields. For each of them, it seems to also know the proper bounds. (I haven't checked to see if these things would be seen if I did not decrypt the document.)

Problem 1: the background graphic will not display from QuickPDF's rendering anymore.

Problem 2: the field titles are all scrambled. I haven't checked Acrobat Pro to make sure it can interpret them correctly still, but since Reader displays the background graphic properly still, I suspect it may.

HJBrown, please understand that PDF1.6 specific dictionaries are not implemented.

Marian,

can yo include my changes to the next version? Maybe it solves the problem hjbrown has.


Urich

Hi,
sorry that I churn up the old thread.
I´ve also this problem (or a other??).
I get a invoise of (strato - is a provider).
I read with acrobat a put a copy in my system. Now I like to read it with the gdpicturepro (isedquichpdf) but the screen will be white???
I´m using the isedquickpdf(5.22.0.119) inside the gdpicturepro (3.03.0001)
Have somebody a solution for me.

Regards Dittmar