(.NET Core C#) RSA Signature/Verify with .key and .cer

See more RSA Examples

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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// 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 .key file:
bool success = privKey.LoadPemFile("privateKey.key");
if (success != true) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

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

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

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

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

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

// Sign the string using the sha-1 hash algorithm.
// Other valid choices are "md2", "sha256", "sha384",
// "sha512", and "md5".
string hexSig = rsa.SignStringENC(strData,"sha-1");

Debug.WriteLine(hexSig);

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

success = cert.LoadFromFile("myCert.cer");
if (success != true) {
    Debug.WriteLine(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) {
    Debug.WriteLine(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) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

Debug.WriteLine("Success.");