Thanks Tilman!
I have tested your code & it works fine 😊
Best regards,
Hesham
--------------------------------------------------------------------------------------------------
Included Message:
here's some code... I'm also adding it to our tests as some extra fun.
PDEncryption encryption = doc.getEncryption();
int revision = encryption.getRevision();
if (revision < 5)
{
StandardSecurityHandler standardSecurityHandler = new
StandardSecurityHandler();
int keyLengthInBytes = encryption.getVersion() == 1 ? 5 :
encryption.getLength() / 8;
byte[] computedUserPassword =
standardSecurityHandler.getUserPassword(
ownerpassword.getBytes(Charsets.ISO_8859_1),
encryption.getOwnerKey(),
revision,
keyLengthInBytes);
}
You could also try to use incremental saving. But it is tricky (you need to set
a "breadcrumb trail" to your updated element(s)) and buggy (if there is a
signature and you don't sign yourself).
Tilman
Am 04.01.2018 um 08:26 schrieb Hesham Gneady:
> Thanks a lot Tilman .. I will try that 😊
>
>
>
> Best regards,
> Hesham
>
> ----------------------------------------------------------------------
> ----------------------------
> Included Message:
>
> It is possible for older encryption (not AES256): get the source code and
> have a look at StandardSecurityHandler.java. There is a segment where
> "isOwnerPassword()" is called, and a bit later, "computedPassword"
> is calculated by calling getUserPassword(). I tried this by debugging with
> out test files and yes I got the user password.
>
> So you could do it by 1) get length, revision and owner key from the
> PDEncryption object you get by calling document.getEncryption() 2) check that
> revision is smaller then 5, and 3) call getUserPassword().
>
> Tilman
>
> Am 03.01.2018 um 09:29 schrieb Hesham Gneady:
>> Hello,
>>
>>
>>
>> I have a PDF file that has an owner password & user password. I'd
>> like to decrypt it using the owner password, make some modifications
>> to it, then encrypt it back and save it. I did the first part
>> successfully, but how can I encrypt it again using the same
>> encryption settings it had, which I don't actually know? . For
>> example, I know only the owner password, but not the user password.
>>
>>
>>
>>
>>
>> Best regards,
>>
>> Hesham
>>
>>
>>
>>
>>
>>
>>
>> ---
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