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Topic: Mistake in PDF spec? (Encryption)
Conf: (P-PDF) Developers, Msg: 54749
From: knewman
Date: 5/29/2002 05:08 PM

There are some inconsitencies, which are causing a few hassles for me.

In the Adobe's PDF Specification 1.3, section 6.13 defines the encryption dictionary.
The P (Permissions) key is defined as an unsigned 32-bit integer. All the PDF files that I've come across only show an unsigned 16-bit value. What should I output in my pdf file?

In computing the U (User) key is calculated using Algorithm 6.7. However, the specification says that Acrobat just uses steps 1 through 3 of Algorithm 6.7 when checking the password. How can this work?

Finally, just a few questions about actually implementing Algorithm 6.7:
There are many different items that are supposed to be put into the MD5 algorithm. Must these items just be added one after each other to form a long string?
Must I use all four bytes of the P (Permissions) key, or just two of them? (see my first question above)
Must I add the file-ID as a sequence of bytes, or as the text representation shown in the file?

Any and all help will be greatly appreciated.


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