(MFC) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

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

See Also: Using MFC CString in Chilkat

#include <CkPrivateKey.h>
#include <CkRsa.h>
#include <CkCert.h>
#include <CkPublicKey.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkPrivateKey pkey;

    // Load the private key from an RSA PEM file:
    bool success = pkey.LoadPkcs8EncryptedFile("raul_privateKey.key","a0123456789");

    const char *pkeyXml = 0;
    // Get the private key in XML format:
    pkeyXml = pkey.getXml();

    CkRsa rsa;

    // Import the private key into the RSA component:
    success = rsa.ImportPrivateKey(pkeyXml);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    rsa.put_EncodingMode("hex");

    const char *strData = "This is the string to be signed.";

    // Sign the string using the sha-1 hash algorithm.
    // Other valid choices are "md2" and "md5".
    const char *hexSig = rsa.signStringENC(strData,"sha-1");

    strOut.append(hexSig);
    strOut.append("\r\n");

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    CkCert cert;
    success = cert.LoadFromFile("raul_publicKey.cer");
    if (success != true) {
        strOut.append(cert.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkPublicKey *pubKey = 0;
    pubKey = cert.ExportPublicKey();

    const char *pubKeyXml = 0;
    // Get the private key in XML format:
    pubKeyXml = pubKey->getXml();

    CkRsa rsa2;
    success = rsa2.ImportPublicKey(pubKeyXml);
    if (success != true) {
        strOut.append(rsa2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Verify the signature against the original data:
    rsa2.put_EncodingMode("hex");
    success = rsa2.VerifyStringENC(strData,"sha-1",hexSig);
    if (success != true) {
        strOut.append(rsa2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Signature verified!");
    strOut.append("\r\n");

    // Verify with incorrect data:
    success = rsa2.VerifyStringENC("something else","sha-1",hexSig);
    if (success != true) {
        strOut.append("Signature not verified! (which was expected in this case)");
        strOut.append("\r\n");
    }
    else {
        strOut.append("Hmmm... that's not right...");
        strOut.append("\r\n");
    }

    delete pubKey;


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }