(C) Load Certificate from Smart Card by Key Usage

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You may have a smartcard or USB token that contains only 2 certificates, one for signing, and one for authentication, and you wish to load the certificate for signing. This example demonstrates how to load the 1st certificate found on a smartcard that matches the intended key usage.

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#include <C_CkCert.h>

void ChilkatSample(void)
    {
    HCkCert cert;
    BOOL success;

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

    cert = CkCert_Create();

    // If you know the smart card PIN, set it prior to loading from the smartcard/USB token.
    CkCert_putSmartCardPin(cert,"12345678");

    // To load a certificate matching an intended key usage, specify the type of usage as shown below.
    // 
    // The possible key usage keywords are:
    // 
    // digitalsignature
    // Use when the public key is used with a digital signature mechanism to support security services other than non-repudiation, certificate signing, or CRL signing. 
    // A digital signature is often used for entity authentication and data origin authentication with integrity.

    // nonrepudiation
    // When a digital certificate's key usage includes "nonrepudiation," it implies that the certificate and its associated private key can be used to 
    // create digital signatures that provide proof of the origin and integrity of the signed data, and the signer cannot later deny having signed the data.

    // Other less common usages:

    // certificatesigning
    // keyencipherment
    // dataencipherment
    // crlsigning
    // secureemail
    // serverauthentication
    // clientauthentication
    // codesigning
    // timestamping

    success = CkCert_LoadFromSmartcard(cert,"keyusage=nonrepudiation");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        printf("Certificate not loaded.\n");
        CkCert_Dispose(cert);
        return;
    }

    printf("Found: %s serial=%s\n",CkCert_subjectDN(cert),CkCert_serialNumber(cert));


    CkCert_Dispose(cert);

    }