(.NET Core C#) ECDSA Sign and Verify Data using Different Hash Algorithms

Demonstrates how to create ECDSA signatures on data using different hash algorithms.

Note: This example requires Chilkat v9.5.0.85 or greater because the SignBd and VerifyBd methods were added in v9.5.0.85.

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

// First load an ECDSA private key to be used for signing.
Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
bool success = privKey.LoadEncryptedPemFile("qa_data/ecc/secp256r1-key-pkcs8-secret.pem","secret");
if (success == false) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

// Load some data to be signed.
Chilkat.BinData bd = new Chilkat.BinData();
success = bd.LoadFile("qa_data/hamlet.xml");
if (success == false) {
    Debug.WriteLine("Failed to load file to be hashed.");
    return;
}

Chilkat.Ecc ecdsa = new Chilkat.Ecc();
Chilkat.Prng prng = new Chilkat.Prng();

// Sign the sha256 hash of the data.  Return the ECDSA signature in the base64 encoding.
Debug.WriteLine("ECDSA signing the sha256 hash of the data...");
string sig = ecdsa.SignBd(bd,"sha256","base64",privKey,prng);
Debug.WriteLine("sig = " + sig);

// Verify the signature against the original data.
// (We must use the same hash algorithm that was used when signing.)

// Load the public key that corresponds to the private key used for signing.
Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pub.pem");
if (success == false) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

Chilkat.Ecc ecc2 = new Chilkat.Ecc();
int result = ecc2.VerifyBd(bd,"sha256",sig,"base64",pubKey);
if (result != 1) {
    Debug.WriteLine(ecc2.LastErrorText);
    return;
}

Debug.WriteLine("Verified!");

// ----------------------------------------------------------------------------------------
// Let's do the same thing, but with sha384 hashing...

Debug.WriteLine("--------------------------------------------");
Debug.WriteLine("ECDSA signing the sha384 hash of the data...");

sig = ecdsa.SignBd(bd,"sha384","base64",privKey,prng);
Debug.WriteLine("sig = " + sig);

result = ecc2.VerifyBd(bd,"sha384",sig,"base64",pubKey);
if (result != 1) {
    Debug.WriteLine(ecc2.LastErrorText);
    return;
}

Debug.WriteLine("Verified!");