(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 <C_CkCrypt2.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    const char *base64Hash;
    HCkCert cert;
    BOOL success;
    const char *base64CmsSig;

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

    crypt = CkCrypt2_Create();

    // Create the hash to be signed...
    CkCrypt2_putHashAlgorithm(crypt,"sha256");
    CkCrypt2_putEncodingMode(crypt,"base64");
    CkCrypt2_putCharset(crypt,"utf-8");
    // Create the SHA256 hash of a string using the utf-8 byte representation.
    // Return the hash as base64.
    base64Hash = CkCrypt2_hashStringENC(crypt,"This is the string to be hashed");

    // Load a certificate for signing.
    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/pfx/cert_test123.pfx","test123");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        return;
    }

    CkCrypt2_SetSigningCert(crypt,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".
    CkCrypt2_putEncodingMode(crypt,"base64_mime");
    base64CmsSig = CkCrypt2_signHashENC(crypt,base64Hash,"sha256","base64");
    if (CkCrypt2_getLastMethodSuccess(crypt) == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        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.

    printf("CMS Signature: %s\n",base64CmsSig);


    CkCrypt2_Dispose(crypt);
    CkCert_Dispose(cert);

    }