C++ 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. C++

#include <CkCert.h>
#include <CkPdf.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    bool 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;
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkPdf pdf;
    success = pdf.LoadFile("qa_data/pdf/two_page_memo.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    //  Encrypt with AES-256 and do not permit modifying.
    pdf.put_UserPassword("user-secret");
    pdf.put_OwnerPassword("owner-secret");
    CkJsonObject json;
    json.UpdateBool("permissions.modify",false);
    CkJsonObject jsonOut;
    success = pdf.Protection("encrypt",json,jsonOut);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    //  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    CkJsonObject sigOpts;
    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) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    //  The result is encrypted and signed.
    CkPdf check;
    check.put_UserPassword("user-secret");
    success = check.LoadFile("qa_output/memo_encrypted_signed.pdf");
    if (success == false) {
        std::cout << check.lastErrorText() << "\r\n";
        return;
    }

    CkJsonObject empty;
    CkJsonObject info;
    success = check.Protection("getInfo",empty,info);
    if (success == false) {
        std::cout << check.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "algorithm: " << info.stringOf("loaded.algorithm") << "\r\n";
    std::cout << "signatures: " << check.get_NumSignatures() << "\r\n";
    CkJsonObject sigInfo;
    bool verified = check.VerifySignature(0,sigInfo);
    std::cout << "signature verifies: " << verified << "\r\n";

    //  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) {
        std::cout << check.lastErrorText() << "\r\n";
        return;
    }

    success = check.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf");
    if (success == false) {
        std::cout << "A second signature was refused: the permissions do not allow it." << "\r\n";
    }

    //  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;
    owner.put_UserPassword("user-secret");
    owner.put_OwnerPassword("owner-secret");
    success = owner.LoadFile("qa_output/memo_encrypted_signed.pdf");
    if (success == false) {
        std::cout << owner.lastErrorText() << "\r\n";
        return;
    }

    success = owner.SetSigningCert(cert);
    if (success == false) {
        std::cout << owner.lastErrorText() << "\r\n";
        return;
    }

    success = owner.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf");
    if (success == false) {
        std::cout << owner.lastErrorText() << "\r\n";
        return;
    }

    CkPdf twice;
    twice.put_UserPassword("user-secret");
    success = twice.LoadFile("qa_output/memo_signed_twice.pdf");
    if (success == false) {
        std::cout << twice.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "signatures after signing with owner rights: " << twice.get_NumSignatures() << "\r\n";
    verified = twice.VerifySignature(0,sigInfo);
    std::cout << "first signature still verifies: " << verified << "\r\n";
    verified = twice.VerifySignature(1,sigInfo);
    std::cout << "second signature verifies: " << verified << "\r\n";

    //  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
    }