Set the Decryption Certificate for an Email

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Demonstrates the Chilkat Email.SetDecryptCert method, which explicitly provides a certificate (with access to its private key) for decrypting a received encrypted email. Set the certificate before loading the encrypted message so Chilkat can decrypt it automatically. This example loads the certificate from a PFX, sets it, and then loads an encrypted email.

Background: Decrypting S/MIME email requires the recipient's private key. On Windows and macOS, Chilkat can find an installed certificate automatically, but when the key lives in a standalone PFX file you provide it explicitly with SetDecryptCert. A PFX (PKCS#12) bundles the certificate and its private key in one password-protected file. If the certificate and key are in separate files, use SetDecryptCert2 instead.

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#include <C_CkEmail.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkEmail email;
    HCkCert cert;

    success = FALSE;

    //  Demonstrates the SetDecryptCert method, which explicitly provides a certificate (with
    //  access to its private key) for decrypting a received encrypted email.  Set the cert
    //  before loading the encrypted email so it can be decrypted automatically.

    email = CkEmail_Create();

    //  Load a certificate together with its private key from a PFX file.
    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/certs/decryption.pfx","pfx_password");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkEmail_Dispose(email);
        CkCert_Dispose(cert);
        return;
    }

    //  Provide the certificate to use for decryption.
    success = CkEmail_SetDecryptCert(email,cert);
    if (success == FALSE) {
        printf("%s\n",CkEmail_lastErrorText(email));
        CkEmail_Dispose(email);
        CkCert_Dispose(cert);
        return;
    }

    //  Load the encrypted email; Chilkat decrypts it using the certificate.
    success = CkEmail_LoadEml(email,"qa_data/eml/encrypted.eml");
    if (success == FALSE) {
        printf("%s\n",CkEmail_lastErrorText(email));
        CkEmail_Dispose(email);
        CkCert_Dispose(cert);
        return;
    }

    printf("ReceivedEncrypted = %d\n",CkEmail_getReceivedEncrypted(email));
    printf("Decrypted = %d\n",CkEmail_getDecrypted(email));

    //  Note: Paths such as "qa_data/..." are relative local filesystem paths,
    //  relative to the current working directory of the running application.


    CkEmail_Dispose(email);
    CkCert_Dispose(cert);

    }