About RSA Public/Private Keys

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Chilkat.Cert cert = new Chilkat.Cert();

bool success;

//  Load a digital certificate.
success = cert.LoadFromFile("digitalCert.cer");
if (success != true) {
    MessageBox.Show(cert.LastErrorText);
    return;
}

Chilkat.PublicKey pubKey = null;

//  A .cer file does not contain the private key.  It should contain
//  the public key...
pubKey = cert.ExportPublicKey();

//  Let's have a look at it (in XML format).
textBox1.Text += "Public Key from Certificate:" + "\r\n";
textBox1.Text += pubKey.GetXml() + "\r\n";

//  An RSA public key consists of a modulus and exponent.

//  An RSA private key includes both the modulus and exponent,
//  as well as other "big" numbers: P, Q, D, etc.

//  Let's load an RSA private key from a DER-encoded file:
Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();

success = privKey.LoadRsaDerFile("PrivateKey.key");
if (success != true) {
    MessageBox.Show(privKey.LastErrorText);
    return;
}

//  If this private key is the matching half to the public key from
//  the certificate, then the modulus and exponent should
//  be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
textBox1.Text += "Private Key from DER:" + "\r\n";
textBox1.Text += privKey.GetXml() + "\r\n";

Chilkat.Rsa rsa = new Chilkat.Rsa();
success = rsa.UnlockComponent("Anything for 30-day trial.");
if (success != true) {
    MessageBox.Show(rsa.LastErrorText);
    return;
}

//  You now realize that the private key really contains both
//  private and public parts.  Therefore, we may import the private
//  key and the choose to use either the public or private in our
//  encrypt/decrypt operations:
string privKeyXml;
privKeyXml = privKey.GetXml();
success = rsa.ImportPrivateKey(privKeyXml);
if (success != true) {
    MessageBox.Show(rsa.LastErrorText);
    return;
}