Áurea,
Áurea Alcaide wrote: > > Thanks Paolo, but is not so easy. Some signatures don't cover all the > document, but continue beeing valid ones. > I think iText does not cover all possible cases involving signature > validation... > >>There's a method in AcroFields to check if the signature covers all the document. >>If it doesn't you may flag it as invalid. > > You are right when you think iText does not cover all possible cases involving signature validation. iText only cares about whether or not the signature correctly signs its byte range. Additionally there is the flag Paulo mentioned. It does not know anything about Adobe's allowed and disallowed changes. You may want to read about them in the Adobe technical white paper "Adobe Acrobat 9 Digital Signatures, Changes and Improvements" available at http://www.adobe.com/devnet/reader/articles/reader_compatibility/readercomp_digitalsignatures.pdf and other documents on that topic. Unfortunately it is not too easy to implement the detection of disallowed changes, and quite likely Adobe will update their algorithms whenever new disallowed changes are found which they don't recognize. Last time I checked it was possible to fool them. Regards, Michael. BTW: PAdES quite recently changed the rules somewhat. -- View this message in context: http://www.nabble.com/PDF-signature-validation-problems-tp25995965p26011472.html Sent from the iText - General mailing list archive at Nabble.com. ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ iText-questions mailing list iText-questions@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/itext-questions Buy the iText book: http://www.1t3xt.com/docs/book.php Check the site with examples before you ask questions: http://www.1t3xt.info/examples/ You can also search the keywords list: http://1t3xt.info/tutorials/keywords/
