Java Requires Chilkat v11.7.0+

Encrypt and Sign a PDF, and Sign an Encrypted PDF

See more PDF Protection Examples

Demonstrates signing together with encryption. A pending encrypt is applied by SignPdf before it signs, so one call produces a PDF that is both encrypted and signed. A PDF that is already encrypted can be signed too, and stays encrypted. When it was opened with only the user password its permissions decide: adding a signature field needs both the modify and the annotate permission. Loading the PDF with its owner password lifts that. Chilkat2 Java

import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.Pdf;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // The PDF used in this example is available at two_page_memo.pdf

        // The signing certificate, with its private key.
        Cert cert = new Cert();
        try {
            cert.loadPfxFile("qa_data/pfx/myPdfSigningCert.pfx", "secret");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        Pdf pdf = new Pdf();
        try {
            pdf.loadFile("qa_data/pdf/two_page_memo.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Encrypt with AES-256 and do not permit modifying.
        pdf.setUserPassword("user-secret");
        pdf.setOwnerPassword("owner-secret");
        JsonObject json = new JsonObject();
        json.updateBool("permissions.modify", false);
        JsonObject jsonOut = new JsonObject();
        try {
            pdf.protection("encrypt", json, jsonOut);

            // The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
            pdf.setSigningCert(cert);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        JsonObject sigOpts = new JsonObject();
        sigOpts.updateBool("invisibleSignature", true);
        sigOpts.updateInt("signingCertificateV2", 1);
        sigOpts.updateInt("signingTime", 1);
        try {
            pdf.signPdf(sigOpts, "qa_output/memo_encrypted_signed.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // The result is encrypted and signed.
        Pdf check = new Pdf();
        check.setUserPassword("user-secret");
        try {
            check.loadFile("qa_output/memo_encrypted_signed.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        JsonObject empty = new JsonObject();
        JsonObject info = new JsonObject();
        try {
            check.protection("getInfo", empty, info);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("algorithm: " + info.stringOf("loaded.algorithm"));
        System.out.println("signatures: " + check.getNumSignatures());
        JsonObject sigInfo = new JsonObject();
        boolean verified;
        try {
            check.verifySignature(0, sigInfo);
            verified = true;
        } catch (ChilkatException e) {
            verified = false;
        }
        System.out.println("signature verifies: " + verified);

        // Signing an encrypted PDF.  This one was opened with only the user password, and its
        // permissions do not allow modifying, so another signature is refused.
        try {
            check.setSigningCert(cert);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        try {
            check.signPdf(sigOpts, "qa_output/memo_signed_twice.pdf");
        } catch (ChilkatException e) {
            System.out.println("A second signature was refused: the permissions do not allow it.");
        }

        // Loaded with the owner password, the same PDF can be signed.  It stays encrypted, and the
        // first signature stays valid because the new one is added as an incremental update.
        Pdf owner = new Pdf();
        owner.setUserPassword("user-secret");
        owner.setOwnerPassword("owner-secret");
        try {
            owner.loadFile("qa_output/memo_encrypted_signed.pdf");

            owner.setSigningCert(cert);

            owner.signPdf(sigOpts, "qa_output/memo_signed_twice.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        Pdf twice = new Pdf();
        twice.setUserPassword("user-secret");
        try {
            twice.loadFile("qa_output/memo_signed_twice.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("signatures after signing with owner rights: " + twice.getNumSignatures());
        try {
            twice.verifySignature(0, sigInfo);
            verified = true;
        } catch (ChilkatException e) {
            verified = false;
        }
        System.out.println("first signature still verifies: " + verified);
        try {
            twice.verifySignature(1, sigInfo);
            verified = true;
        } catch (ChilkatException e) {
            verified = false;
        }
        System.out.println("second signature verifies: " + verified);

        // Sample output:

        // algorithm: aes-256
        // signatures: 1
        // signature verifies: True
        // A second signature was refused: the permissions do not allow it.
        // signatures after signing with owner rights: 2
        // first signature still verifies: True
        // second signature verifies: True
    }
}