RSA Signature/Verify with .key and .cer

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

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Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();

bool success;

//  Load the private key from an RSA .key file:
success = privKey.LoadPemFile("privateKey.key");
if (success != true) {
    MessageBox.Show(privKey.LastErrorText);
    return;
}

string privKeyXml;
//  Get the private key in XML format:
privKeyXml = privKey.GetXml();

Chilkat.Rsa rsa = new Chilkat.Rsa();

//  Any string argument automatically begins the 30-day trial.

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

//  Import the private key into the RSA component:
success = rsa.ImportPrivateKey(privKeyXml);
if (success != true) {
    MessageBox.Show(rsa.LastErrorText);
    return;
}

//  Create the signature as a hex string:
rsa.EncodingMode = "hex";

string strData;
strData = "This is the string to be signed.";

//  Sign the string using the sha-1 hash algorithm.
//  Other valid choices are "md2" and "md5".
string hexSig;
hexSig = rsa.SignStringENC(strData,"sha-1");

textBox1.Text += hexSig + "\r\n";

//  Load a digital certificate from a .cer file:
Chilkat.Cert cert = new Chilkat.Cert();

success = cert.LoadFromFile("myCert.cer");
if (success != true) {
    MessageBox.Show(cert.LastErrorText);
    return;
}

Chilkat.PublicKey pubKey = null;

pubKey = cert.ExportPublicKey();

//  Now verify using a separate instance of the RSA object:
Chilkat.Rsa rsa2 = new Chilkat.Rsa();

//  Import the public key into the RSA object:
success = rsa2.ImportPublicKey(pubKey.GetXml());
if (success != true) {
    MessageBox.Show(rsa2.LastErrorText);
    return;
}

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

//  Verify the signature:
success = rsa2.VerifyStringENC(strData,"sha-1",hexSig);
if (success != true) {
    MessageBox.Show(rsa2.LastErrorText);
    return;
}

MessageBox.Show("Success.");