(C) Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how 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.

Chilkat C/C++ Library Downloads
MS Visual C/C++ Linux/CentOS C/C++ Alpine Linux C/C++ MAC OS X C/C++	armhf/aarch64 C/C++ C++ Builder iOS C/C++ Android C/C++	Solaris C/C++ MinGW C/C++

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

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

    // 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 PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
    // This example will load the certificate from a .crt and the private key from a .key file

    cert = CkCert_Create();
    // The LoadFromFile method will automatically detect the format and load it.
    success = CkCert_LoadFromFile(cert,"qa_data/certs/test_12345678a.cer");
    if (success != TRUE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        return;
    }

    // Our private key is in an encrypted PKCS8 format.
    // If you don't know the format of your key, but you do know it's encrypted,
    // and requires a password, then just call any of the Chilkat methods that load
    // a private key w/ a password argument.  Chilkat will auto-detect the format
    // and load it correctly even if it's not the format indicated by the method name..
    privKey = CkPrivateKey_Create();
    password = "12345678a";
    success = CkPrivateKey_LoadPkcs8EncryptedFile(privKey,"qa_data/certs/test_12345678a.key",password);
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    // Set properties required for signing.

    // Tell it to use the cert and private key we've loaded.
    success = CkCrypt2_SetSigningCert2(crypt,cert,privKey);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert);
        CkPrivateKey_Dispose(privKey);
        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);
        CkPrivateKey_Dispose(privKey);
        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();

    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);
        CkPrivateKey_Dispose(privKey);
        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);
    CkPrivateKey_Dispose(privKey);
    CkCrypt2_Dispose(vCrypt);

    }