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. Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  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.
    CkCert cert = new CkCert();
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret");
    if (success == false) {
        System.out.println(cert.lastErrorText());
        return;
        }

    CkPdf pdf = new CkPdf();
    success = pdf.LoadFile("qa_data/pdf/two_page_memo.pdf");
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    //  Encrypt with AES-256 and do not permit modifying.
    pdf.put_UserPassword("user-secret");
    pdf.put_OwnerPassword("owner-secret");
    CkJsonObject json = new CkJsonObject();
    json.UpdateBool("permissions.modify",false);
    CkJsonObject jsonOut = new CkJsonObject();
    success = pdf.Protection("encrypt",json,jsonOut);
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    //  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    CkJsonObject sigOpts = new CkJsonObject();
    sigOpts.UpdateBool("invisibleSignature",true);
    sigOpts.UpdateInt("signingCertificateV2",1);
    sigOpts.UpdateInt("signingTime",1);
    success = pdf.SignPdf(sigOpts,"qa_output/memo_encrypted_signed.pdf");
    if (success == false) {
        System.out.println(pdf.lastErrorText());
        return;
        }

    //  The result is encrypted and signed.
    CkPdf check = new CkPdf();
    check.put_UserPassword("user-secret");
    success = check.LoadFile("qa_output/memo_encrypted_signed.pdf");
    if (success == false) {
        System.out.println(check.lastErrorText());
        return;
        }

    CkJsonObject empty = new CkJsonObject();
    CkJsonObject info = new CkJsonObject();
    success = check.Protection("getInfo",empty,info);
    if (success == false) {
        System.out.println(check.lastErrorText());
        return;
        }

    System.out.println("algorithm: " + info.stringOf("loaded.algorithm"));
    System.out.println("signatures: " + check.get_NumSignatures());
    CkJsonObject sigInfo = new CkJsonObject();
    boolean verified = check.VerifySignature(0,sigInfo);
    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.
    success = check.SetSigningCert(cert);
    if (success == false) {
        System.out.println(check.lastErrorText());
        return;
        }

    success = check.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf");
    if (success == false) {
        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.
    CkPdf owner = new CkPdf();
    owner.put_UserPassword("user-secret");
    owner.put_OwnerPassword("owner-secret");
    success = owner.LoadFile("qa_output/memo_encrypted_signed.pdf");
    if (success == false) {
        System.out.println(owner.lastErrorText());
        return;
        }

    success = owner.SetSigningCert(cert);
    if (success == false) {
        System.out.println(owner.lastErrorText());
        return;
        }

    success = owner.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf");
    if (success == false) {
        System.out.println(owner.lastErrorText());
        return;
        }

    CkPdf twice = new CkPdf();
    twice.put_UserPassword("user-secret");
    success = twice.LoadFile("qa_output/memo_signed_twice.pdf");
    if (success == false) {
        System.out.println(twice.lastErrorText());
        return;
        }

    System.out.println("signatures after signing with owner rights: " + twice.get_NumSignatures());
    verified = twice.VerifySignature(0,sigInfo);
    System.out.println("first signature still verifies: " + verified);
    verified = twice.VerifySignature(1,sigInfo);
    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
  }
}