(C++) CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

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#include <CkCrypt2.h>
#include <CkCert.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkCrypt2 crypt;

    // Create the hash to be signed...
    crypt.put_HashAlgorithm("sha256");
    crypt.put_EncodingMode("base64");
    crypt.put_Charset("utf-8");
    // Create the SHA256 hash of a string using the utf-8 byte representation.
    // Return the hash as base64.
    const char *base64Hash = crypt.hashStringENC("This is the string to be hashed");

    // Load a certificate for signing.
    CkCert cert;
    bool success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    crypt.SetSigningCert(cert);

    // Sign the hash to create a base64 CMS signature (which does not contain the original data).
    // We can get the signature in a single line of base64 by specifying "base64", or 
    // we can get multi-line base64 by specifying "base64_mime".
    crypt.put_EncodingMode("base64_mime");
    const char *base64CmsSig = crypt.signHashENC(base64Hash,"sha256","base64");
    if (crypt.get_LastMethodSuccess() == false) {
        std::cout << crypt.lastErrorText() << "\r\n";
        return;
    }

    // Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
    // However, the encoding of the passed-in hash is indicated by the 3rd argument.

    std::cout << "CMS Signature: " << base64CmsSig << "\r\n";
    }