C

A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

See more Digital Signatures Examples

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token to create a PKCS7 opaque signature, and also how to verify an opaque signature.

An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

C

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

void ChilkatSample(void)
    {
    BOOL success;
    HCkCrypt2 crypt;
    HCkCert cert;
    const char *originalData;
    const char *opaqueSig;
    HCkCrypt2 vCrypt;
    const char *extractedData;

    success = FALSE;

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

    crypt = CkCrypt2_Create();

    //  A certificate and private key is needed to create a signature.
    //  Chilkat provides many different ways to load a certificate and private key, such
    //  as from a smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
    //  This example will load the default certificate from the smartcard that is currently in
    //  the smartcard reader.

    cert = CkCert_Create();

    //  If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
    CkCert_putSmartCardPin(cert,"000000");

    success = CkCert_LoadFromSmartcard(cert,"");
    if (success != TRUE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        return;
    }

    //  Tell it to use the cert and private key we've loaded.
    success = CkCrypt2_SetSigningCert(crypt,cert);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        return;
    }

    //  Indicate we want the opaque signature in base64 format:
    CkCrypt2_putEncodingMode(crypt,"base64");

    //  Sign the string using the "utf-8" byte representation:
    CkCrypt2_putCharset(crypt,"utf-8");

    //  Create the opaque signature:
    originalData = "This is the string to be signed.";
    opaqueSig = CkCrypt2_opaqueSignStringENC(crypt,originalData);
    if (CkCrypt2_getLastMethodSuccess(crypt) != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        return;
    }

    printf("%s\n",opaqueSig);

    //  The output looks like this:
    //  MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

    //  ----------------------------------------------------------------------------------------------
    //  Now let's verify the signature and retrieve the original data.
    //  We'll use a new Crypt2 object to keep things completely separate...

    vCrypt = CkCrypt2_Create();

    //  We only need the certificate to verify a signature (and extract the data from
    //  an opaque signature).  The public key is always embedded within a certificate.
    success = CkCrypt2_SetVerifyCert(vCrypt,cert);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(vCrypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        CkCrypt2_Dispose(vCrypt);
        return;
    }

    CkCrypt2_putEncodingMode(vCrypt,"base64");
    CkCrypt2_putCharset(vCrypt,"utf-8");

    extractedData = CkCrypt2_opaqueVerifyStringENC(vCrypt,opaqueSig);
    if (CkCrypt2_getLastMethodSuccess(vCrypt) != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(vCrypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        CkCrypt2_Dispose(vCrypt);
        return;
    }

    printf("The extracted data: %s\n",extractedData);

    //  The output is:
    //  The extracted data: This is the string to be signed.


    CkCrypt2_Dispose(crypt);
    CkCert_Dispose(cert);
    CkCrypt2_Dispose(vCrypt);

    }