(C++) Convert RSA Private Key to Public Key

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

Note: This example requires Chilkat v11.0.0 or greater.

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

void ChilkatSample(void)
    {
    bool success = false;

    CkPrivateKey privKey;

    // 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.)
    success = privKey.LoadPemFile("qa_data/pem/VP_Private.pem");
    if (success == false) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    // Step 2: Get the public key object from the private key object.
    CkPublicKey pubKey;
    privKey.ToPublicKey(pubKey);

    // 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() == false) {
        std::cout << pubKey.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Extracted and saved public key from private key." << "\r\n";
    }