Add a Detached Signature with a Separate Private Key

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Demonstrates the Chilkat Mime.AddDetachedSignaturePk method, which creates a detached signature using a signer certificate and its separately supplied private key. The first argument is the Cert and the second is the PrivateKey.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Sometimes the certificate and its private key live apart — a .cer alongside a PEM key file, for instance — rather than bundled in a single PFX. This method pairs them explicitly for signing, whereas AddDetachedSignature expects a Cert that already provides its key. The result is the same multipart/signed message.

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#include <C_CkMime.h>
#include <C_CkCert.h>
#include <C_CkPrivateKey.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkMime mime;
    HCkCert cert;
    HCkPrivateKey privKey;

    success = FALSE;

    mime = CkMime_Create();
    success = CkMime_SetBodyFromPlainText(mime,"This message will be signed.");
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        return;
    }

    //  Load the certificate and its private key separately.
    cert = CkCert_Create();
    success = CkCert_LoadFromFile(cert,"qa_data/signer.cer");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkMime_Dispose(mime);
        CkCert_Dispose(cert);
        return;
    }

    privKey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadPemFile(privKey,"qa_data/signer_privkey.pem");
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkMime_Dispose(mime);
        CkCert_Dispose(cert);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    //  Create a detached signature when the certificate and private key are supplied separately.  The
    //  1st argument is the signer certificate and the 2nd is its private key.
    success = CkMime_AddDetachedSignaturePk(mime,cert,privKey);
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        CkCert_Dispose(cert);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    success = CkMime_SaveMime(mime,"qa_output/signed.eml");
    if (success == FALSE) {
        printf("%s\n",CkMime_lastErrorText(mime));
        CkMime_Dispose(mime);
        CkCert_Dispose(cert);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    printf("Detached signature added.\n");


    CkMime_Dispose(mime);
    CkCert_Dispose(cert);
    CkPrivateKey_Dispose(privKey);

    }