Robert,
please reply to the list.
RobertQ wrote:
>
> How are you? You repplied my post "Verifying signature!!
> NoSuchAlgorithmException: 1.2.840.113549.1.1.1" suggesting me this:
>
> mkl wrote:
>>
>> Use the AcroFields methods getSignatureNames and getSignatureDictionary.
>> The latter dictionary contains the signature container (key:
>> PdfName.CONTENTS, apply getOriginalBytes) and the range data (key:
>> PdfName.BYTERANGE). Use something like the class
>> PdfSignatureAppearance.RangeStream to extract the signed data.
>>
>
> What I tryied to do is the following:
>
> PdfReader reader = new PdfReader(new
> RandomAccessFileOrArray("temp.pdf"), null);
> AcroFields acrFs = reader.getAcroFields();
>
> PdfDictionary dic = acrFs.getSignatureDictionary("Signature1");
>
> PdfObject sigContainer = dic.get(PdfName.CONTENTS);
> PdfObject rangeData = dic.get(PdfName.BYTERANGE);
>
> But it didn't work out, I stopped at this point.
> Can you send me an example code of what you suggested.
>
What exactly didn't work out?
Obviously you have to inspect the individual attributes more thoroughly,
e.g.:
((PdfString)PdfReader.getPdfObject(dic.get(PdfName.CONTENTS))).getOriginalBytes()
contains the signature container and some trailing debris, most often filled
with 0 bytes.
(PdfArray)PdfReader.getPdfObject(dic.get(PdfName.BYTERANGE)) will give you
the byterange array; you might want to use this array in concert with a
class like PdfSignatureAppearance.RangeStream to extract the signed data
stream.
And obviously you should do some sanity checks (e.g. for null values) in
production code...
Regards, Mikel.
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