(MFC) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

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

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

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

    // Load an RSA private key for signing.
    CkPrivateKey privKey;
    bool success = privKey.LoadEncryptedPemFile("qa_data/pem/rsa_passwd.pem","passwd");
    if (success != true) {
        strOut.append(privKey.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkRsa rsa;
    rsa.ImportPrivateKeyObj(privKey);

    // We have some binary data (in hex) to sign
    const char *originalData = "0102030405060708090A";
    CkBinData bd;
    bd.AppendEncoded(originalData,"hex");

    // If successful, the contents of bd are replaced with the RSA signature.
    success = rsa.OpenSslSignBd(bd);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the RSA signature in base64
    strOut.append(bd.getEncoded("base64"));
    strOut.append("\r\n");

    // ------------------------------------------
    // Get the public key from the private key
    CkPublicKey *pubKey = privKey.GetPublicKey();

    // Verify the signature and extract the original data.
    CkRsa rsa2;
    rsa2.ImportPublicKeyObj(*pubKey);

    bool bVerified = rsa2.OpenSslVerifyBd(bd);
    strOut.append("signature verified: ");
    strOut.appendInt(bVerified);
    strOut.append("\r\n");

    // Show the original data:
    strOut.append("original data: ");
    strOut.append(bd.getEncoded("hex"));
    strOut.append("\r\n");

    delete pubKey;


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }