twain,

twain wrote:
> Now I need to add a new entry to the exclusions HashMap, because I need to
> insert new data excluded from hash computation.
> 
> But if I try to do:
> 
> [...]
> 
> I obtain a pdf that cause a problem in Adobe Reader about
> SigDict/ByteRange value.
> 
> [...]
> 
> Where am I wrong?

You are wrong in assuming that integrated PDF signatures covering less than
everything but the signature container itself are accepted by the Adobe
Acrobat or Reader.

While it is ok according to the original PDF specifications to exclude more
than just the signature container from the hash value calculation, Adobe
Reader and Acrobat do not accept such limitted signed ranges. The reason is
fairly obvious; if you exclude anything but the signature container from
hashing, that other part can be changed without breaking the signature.
Thus, the signature is meaningless unless you do an in-depth analysis of the
document parts actually signed and mark them upon display or evaluation.

BTW, in newer specifications, e.g. for PAdES, the signed byte range is
required to be the entire file, including the signature dictionary but
excluding the signature container itself.

If you really need a place to transport dynamic contents, you may want to
add them as unsigned attributes of the signature container.

Regards,   Michael

--
View this message in context: 
http://itext-general.2136553.n4.nabble.com/Problem-with-preClose-function-and-exclusion-hashmap-tp3903958p3904046.html
Sent from the iText - General mailing list archive at Nabble.com.

------------------------------------------------------------------------------
All the data continuously generated in your IT infrastructure contains a
definitive record of customers, application performance, security
threats, fraudulent activity and more. Splunk takes this data and makes
sense of it. Business sense. IT sense. Common sense.
http://p.sf.net/sfu/splunk-d2d-oct
_______________________________________________
iText-questions mailing list
iText-questions@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/itext-questions

iText(R) is a registered trademark of 1T3XT BVBA.
Many questions posted to this list can (and will) be answered with a reference 
to the iText book: http://www.itextpdf.com/book/
Please check the keywords list before you ask for examples: 
http://itextpdf.com/themes/keywords.php

Reply via email to