(MFC) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkCrypt2 crypt;

    // Get a digital certificate with private key from a .pfx
    // (Chilkat has many different ways to provide a cert + private key for siging.
    // Using a PFX is just one possible option.)
    CkPfx pfx;
    bool success = pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
    if (success != true) {
        strOut.append(pfx.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Get the certificate to be used for signing.
    // (The typical case for a PFX is that it contains a cert with an associated private key,
    // as well as other certificates in the chain of authentication.  The cert with the private
    // key should be in the first position at index 0.)
    CkCert *cert = pfx.GetCert(0);
    if (pfx.get_LastMethodSuccess() != true) {
        strOut.append(pfx.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    crypt.SetSigningCert(*cert);

    // Indicate that RSASSA-PSS with SHA256 should be used.
    crypt.put_SigningAlg("pss");
    crypt.put_HashAlgorithm("sha256");

    crypt.put_EncodingMode("base64");

    // Sign a string and return the base64 PKCS7 detached signature
    const char *originalText = "This is a test";
    const char *pkcs7sig = crypt.signStringENC(originalText);
    strOut.append("Detached Signature:");
    strOut.append("\r\n");
    strOut.append(pkcs7sig);
    strOut.append("\r\n");

    // This signature looks like this:
    // MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // The signature can be verified against the original data like this:
    success = crypt.VerifyStringENC(originalText,pkcs7sig);
    strOut.append("Signature verified: ");
    strOut.appendInt(success);
    strOut.append("\r\n");
    success = crypt.VerifyStringENC("Not the original text",pkcs7sig);
    strOut.append("Signature verified: ");
    strOut.appendInt(success);
    strOut.append("\r\n");

    // Now we'll create an opaque signature (the opposite of a detached signature). 
    // An opaque signature is a PKCS7 message that contains both the original data and
    // the signature.  The verification process extracts the original data.
    const char *opaqueSig = crypt.opaqueSignStringENC(originalText);
    strOut.append("Opaque Signature:");
    strOut.append("\r\n");
    strOut.append(opaqueSig);
    strOut.append("\r\n");

    // The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
    // then copy-and-paste the Base64 signature into the form and decode..

    // We can verify and extract the original data:
    const char *origTxt = crypt.opaqueVerifyStringENC(opaqueSig);
    if (crypt.get_LastMethodSuccess() != true) {
        strOut.append("Signature verification failed.");
        strOut.append("\r\n");
        strOut.append(crypt.lastErrorText());
        strOut.append("\r\n");
        delete cert;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Signature verified.");
    strOut.append("\r\n");
    strOut.append("Extracted text:");
    strOut.append(origTxt);
    strOut.append("\r\n");

    delete cert;


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }