(MFC) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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 privKey;

    // Load the private key from an RSA .key file:
    bool success = privKey.LoadPemFile("privateKey.key");
    if (success != true) {
        strOut.append(privKey.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

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

    CkRsa rsa;

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

    // Create the signature as a hex string:
    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", "sha256", "sha384",
    // "sha512", and "md5".
    const char *hexSig = rsa.signStringENC(strData,"sha-1");

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

    // Load a digital certificate from a .cer file:
    CkCert cert;

    success = cert.LoadFromFile("myCert.cer");
    if (success != true) {
        strOut.append(cert.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkPublicKey *pubKey = 0;

    pubKey = cert.ExportPublicKey();

    // Now verify using a separate instance of the RSA object:
    CkRsa rsa2;

    // Import the public key into the RSA object:
    success = rsa2.ImportPublicKey(pubKey->getXml());
    if (success != true) {
        strOut.append(rsa2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    delete pubKey;

    // The signature is a hex string, so make sure the EncodingMode is correct:
    rsa2.put_EncodingMode("hex");

    // Verify the signature:
    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("Success.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }