(MFC) Convert RSA Private Key to Public Key

Demonstrates how to get a public RSA key from a private RSA key.

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

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

    CkPrivateKey key;

    // Step 1: Load the private key from a source.
    // (Chilkat can load private keys from all types of formats, and from in-memory bytes or encoded strings.
    // see the online reference documentation for more options.)
    bool success = key.LoadPemFile("qa_data/pem/VP_Private.pem");
    if (success != true) {
        strOut.append(key.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Step 2: Get the public key object from the private key object.
    CkPublicKey *pubKey = key.GetPublicKey();
    if (key.get_LastMethodSuccess() != true) {
        strOut.append(key.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Step 3: Save the public key in a desired format. 
    // (Chilkat can load or save public and private keys in many different formats.  See
    // the online reference documentation for more options.)

    // Saves to a PKCS8 PEM file.
    bool bPreferPkcs1 = false;
    success = pubKey->SavePemFile(bPreferPkcs1,"qa_data/pem/VP_Public.pem");
    if (pubKey->get_LastMethodSuccess() != true) {
        strOut.append(pubKey->lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    delete pubKey;

    strOut.append("Extracted and saved public key from private key.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }