Because object numbering and their location in a PDF are completely free form –
there are no requirements.
Why does it matter?
From: Alvaro Cuno <[email protected]<mailto:[email protected]>>
Reply-To: Post here
<[email protected]<mailto:[email protected]>>
To: Post here
<[email protected]<mailto:[email protected]>>
Subject: [iText-questions] are the dictionary elements randomly placed?
Hello all,
I signed a same file (hello.pdf) three times using the next code:
public static void sign(String src, String dest)
throws IOException, DocumentException, KeyStoreException,
NoSuchAlgorithmException, CertificateException,
UnrecoverableKeyException {
Security.addProvider(new BouncyCastleProvider());
KeyStore ks = KeyStore.getInstance("pkcs12");
ks.load(new FileInputStream("citizen1.p12"), "password".toCharArray());
String alias = (String) ks.aliases().nextElement();
PrivateKey key = (PrivateKey) ks.getKey(alias,
"password".toCharArray());
Certificate[] chain = ks.getCertificateChain(alias);
PdfReader reader = new PdfReader(src);
FileOutputStream os = new FileOutputStream(dest);
PdfStamper stamper = PdfStamper.createSignature(reader, os, '\0', null,
true);
PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
appearance.setAcro6Layers(true);
appearance.setCrypto(key, chain, null,
PdfSignatureAppearance.WINCER_SIGNED);
appearance.setVisibleSignature(new Rectangle(160, 732, 232, 780), 1,
null);
Calendar cal = Calendar.getInstance();
cal.setTime(new Date(0));
appearance.setSignDate(cal);
stamper.close();
}
Everything is ok and all digital signatures are valid, however I don't
understand why the internal structures of the signed documents (see attached
files) are different?
hello-signed-1.pdf hello-signed-2.pdf hello-signed-3.pdf
... ... ...
%%EOF %%EOF %%EOF
... ... ...
10 0 obj 10 0 obj 10 0 obj
11 0 obj 8 0 obj 11 0 obj
12 0 obj 11 0 obj 12 0 obj
8 0 obj 9 0 obj 9 0 obj
9 0 obj 12 0 obj 8 0 obj
5 0 obj 5 0 obj 5 0 obj
... ... ...
The objects 8, 9 and 11 are related to /n0, /n2, /FRM fields, ... these were
inserted randomly? if yes, why?
-
Alvaro
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