Unicode C Requires Chilkat v11.7.0+

Encrypt a PDF for a Certificate Instead of a Password

Demonstrates certificate security, where a PDF is encrypted for one or more recipients and each opens it with their own certificate and private key. No password is involved. Only the public certificate of a recipient is needed to encrypt. Each recipient has its own permissions, and the changeSecurity permission gives a recipient owner rights. PreLoadCheck tells an application that a file is certificate-encrypted and which certificates can open it. A PDF that cannot be opened, because no matching certificate and private key were provided, fails to load.

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Unicode C

#include <C_CkCertW.h>
#include <C_CkPdfW.h>
#include <C_CkJsonObjectW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCertW recipient;
    HCkPdfW pdf;
    HCkJsonObjectW json;
    HCkJsonObjectW jsonOut;
    HCkPdfW reader;
    HCkJsonObjectW info;
    HCkCertW myCert;
    HCkJsonObjectW empty;
    HCkJsonObjectW loadedInfo;

    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 recipient's certificate.  Only the public certificate is needed to encrypt.
    recipient = CkCertW_Create();
    success = CkCertW_LoadFromFile(recipient,L"qa_data/certs/recipient.cer");
    if (success == FALSE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(recipient));
        CkCertW_Dispose(recipient);
        return;
    }

    pdf = CkPdfW_Create();
    success = CkPdfW_LoadFile(pdf,L"qa_data/pdf/two_page_memo.pdf");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        return;
    }

    //  Call AddEncryptCert once for each recipient.
    success = CkPdfW_AddEncryptCert(pdf,recipient);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        return;
    }

    //  recipientPermissions[0] belongs to the first certificate added.  changeSecurity gives that
    //  recipient owner rights, so the file can be managed later.
    json = CkJsonObjectW_Create();
    CkJsonObjectW_UpdateString(json,L"method",L"certificate");
    CkJsonObjectW_UpdateBool(json,L"recipientPermissions[0].changeSecurity",TRUE);

    jsonOut = CkJsonObjectW_Create();
    success = CkPdfW_Protection(pdf,L"encrypt",json,jsonOut);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        return;
    }

    wprintf(L"method: %s\n",CkJsonObjectW_stringOf(jsonOut,L"pending.method"));
    wprintf(L"algorithm: %s\n",CkJsonObjectW_stringOf(jsonOut,L"pending.algorithm"));
    wprintf(L"recipients: %d\n",CkJsonObjectW_SizeOfArray(jsonOut,L"pending.recipients"));

    success = CkPdfW_WriteFile(pdf,L"qa_output/memo_for_recipient.pdf");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        return;
    }

    //  PreLoadCheck says how the file is protected, without loading it.
    reader = CkPdfW_Create();
    info = CkJsonObjectW_Create();
    success = CkPdfW_PreLoadCheck(reader,L"qa_output/memo_for_recipient.pdf",info);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(reader));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        CkPdfW_Dispose(reader);
        CkJsonObjectW_Dispose(info);
        return;
    }

    wprintf(L"saved file, method: %s\n",CkJsonObjectW_stringOf(info,L"method"));
    wprintf(L"saved file, recipients: %d\n",CkJsonObjectW_SizeOfArray(info,L"recipients"));

    //  The recipient opens it with the certificate and its private key, here from a .pfx file.
    //  (On Windows, a certificate that is installed in the Windows certificate store with its private
    //  key is found automatically when the PDF is loaded, and SetDecryptCert is not needed for it.)
    myCert = CkCertW_Create();
    success = CkCertW_LoadPfxFile(myCert,L"qa_data/pfx/recipient.pfx",L"pfx-password");
    if (success == FALSE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(myCert));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        CkPdfW_Dispose(reader);
        CkJsonObjectW_Dispose(info);
        CkCertW_Dispose(myCert);
        return;
    }

    success = CkPdfW_SetDecryptCert(reader,myCert);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(reader));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        CkPdfW_Dispose(reader);
        CkJsonObjectW_Dispose(info);
        CkCertW_Dispose(myCert);
        return;
    }

    success = CkPdfW_LoadFile(reader,L"qa_output/memo_for_recipient.pdf");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(reader));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        CkPdfW_Dispose(reader);
        CkJsonObjectW_Dispose(info);
        CkCertW_Dispose(myCert);
        return;
    }

    empty = CkJsonObjectW_Create();
    loadedInfo = CkJsonObjectW_Create();
    success = CkPdfW_Protection(reader,L"getInfo",empty,loadedInfo);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(reader));
        CkCertW_Dispose(recipient);
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkJsonObjectW_Dispose(jsonOut);
        CkPdfW_Dispose(reader);
        CkJsonObjectW_Dispose(info);
        CkCertW_Dispose(myCert);
        CkJsonObjectW_Dispose(empty);
        CkJsonObjectW_Dispose(loadedInfo);
        return;
    }

    wprintf(L"opened with: %s\n",CkJsonObjectW_stringOf(loadedInfo,L"loaded.openedWith"));
    wprintf(L"pages: %d\n",CkPdfW_getNumPages(reader));

    //  Sample output:

    //  method: certificate
    //  algorithm: aes-256
    //  recipients: 1
    //  saved file, method: certificate
    //  saved file, recipients: 1
    //  opened with: certificate
    //  pages: 2


    CkCertW_Dispose(recipient);
    CkPdfW_Dispose(pdf);
    CkJsonObjectW_Dispose(json);
    CkJsonObjectW_Dispose(jsonOut);
    CkPdfW_Dispose(reader);
    CkJsonObjectW_Dispose(info);
    CkCertW_Dispose(myCert);
    CkJsonObjectW_Dispose(empty);
    CkJsonObjectW_Dispose(loadedInfo);

    }