C++

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

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: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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C++

#include <CkMime.h>
#include <CkCert.h>

void ChilkatSample(void)
    {
    bool success = false;

    CkMime mime;
    success = mime.SetBodyFromPlainText("This message will be signed.");
    if (success == false) {
        std::cout << mime.lastErrorText() << "\r\n";
        return;
    }

    //  Load the signing certificate (which must have access to its private key) from a PFX file.
    //  The PFX password should come from a secure source rather than being hard-coded.
    const char *pfxPassword = "myPfxPassword";
    CkCert cert;
    success = cert.LoadPfxFile("qa_data/signer.pfx",pfxPassword);
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    //  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
    //  original content and a separate signature part.
    success = mime.AddDetachedSignature(cert);
    if (success == false) {
        std::cout << mime.lastErrorText() << "\r\n";
        return;
    }

    success = mime.SaveMime("qa_output/signed.eml");
    if (success == false) {
        std::cout << mime.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Detached signature added." << "\r\n";
    }