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

See more RSA Examples

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

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

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 .key file:
success = privKey.LoadPemFile("privateKey.key");
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;
}

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

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

// Sign the string using the sha256 hash algorithm.
// Other valid choices are "md2", "sha1", "sha384",
// "sha512", and "md5".
string hexSig = rsa.SignStringENC(strData,"sha256");

Debug.WriteLine(hexSig);

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

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

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

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

// Import the public key into the RSA object:
success = rsa2.UsePublicKey(pubKey);
if (success == false) {
    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,"sha256",hexSig);
if (success == false) {
    Debug.WriteLine(rsa2.LastErrorText);
    return;
}

Debug.WriteLine("Success.");