(C#) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

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

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bool success = false;

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

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

// Load the private key from an RSA PEM file:
success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789");
if (success == false) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

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

// Import the private key into the RSA component:
success = rsa.UsePrivateKey(privKey);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

// This example will sign a string, and receive the signature
// in a hex-encoded string.  Therefore, set the encoding mode
// to "hex":
rsa.EncodingMode = "hex";

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

// Sign the string using the sha256 hash algorithm.
// Other valid choices are sha1, sha384, sha512 and others.
string hexSig = rsa.SignStringENC(strData,"sha256");
if (rsa.LastMethodSuccess == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

Debug.WriteLine(hexSig);

// Now verify with the public key.
// This example shows how to use the public key from 
// a digital certificate (.cer file)
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadFromFile("raul_publicKey.cer");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
cert.GetPublicKey(pubKey);

Chilkat.Rsa rsa2 = new Chilkat.Rsa();
success = rsa2.UsePublicKey(pubKey);
if (success == false) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

// Verify the signature against the original data:
rsa2.EncodingMode = "hex";
success = rsa2.VerifyStringENC(strData,"sha256",hexSig);
if (success == false) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

Debug.WriteLine("Signature verified!");

// Verify with incorrect data:
success = rsa2.VerifyStringENC("something else","sha256",hexSig);
if (success != true) {
    Debug.WriteLine("Signature not verified! (which was expected in this case)");
}
else {
    Debug.WriteLine("Hmmm... that's not right...");
}