How to sign a pdf with XML signature [closed]

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I'm working on an Java application for digital signature and timestamping PDFs, using iText and BouncyCastle.

The problem is that we have to make a timestamp with a XML signature received from a web service.

Anyone know if this is possible to do it?.

Kind regards.

Answer 1

In a nutshell:

Integrated PDF time stamps require RFC3161 time stamps (if time stamping is desired at all).

In detail:

In case of time stamped signatures according to ISO 32000-1 (which still is the current PDF standard), the signature container can contain:

Time stamp information as an unsigned attribute (PDF 1.6): The timestamp token shall conform to RFC 3161 and shall be computed and embedded into the PKCS#7 object as described in Appendix A of RFC 3161. The specific treatment of timestamps and their processing is left to the particular signature handlers to define.

(section 12.8.3.3.1)

In case of the document time stamps according to the PAdES LTV profile from ETSI TS 102 778 part 4 extending the standard, the document time stamp value

shall be the TimeStampToken as specified in RFC 3161 [6].

(Annex A.2)

Thus, for you to be able to create interoperable PDF time stamps, your service must provide RFC 3161 time stamps.

ETSI TS 102 778 part 5 allows XML time stamps, but they can only be used

• for XAdES signatures of signed XML documents embedded in PDF containers (section 4) and
• for XAdES signatures on XFA Forms (section 5).

Neither of those stamps the PDF as such.