(.NET Core C#) ECDSA Sign Data and Verify Signature

Demonstrates using the Elliptic Curve Digital Signature Algorithm to hash data and sign it. Also demonstrates how to verify the ECDSA signature.

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

// To create an ECDSA signature, the data first needs to be hashed.  Then the hash
// is signed.

// Use Chilkat Crypt2 to generate a hash for any of the following
// hash algorithms: SHA256, SHA384, SHA512, SHA1, MD5, MD2, HAVAL, RIPEMD128/160/256/320

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();
crypt.HashAlgorithm = "SHA256";
crypt.Charset = "utf-8";
crypt.EncodingMode = "base64";

// Hash a string.
string hash1 = crypt.HashStringENC("The quick brown fox jumps over the lazy dog");
Debug.WriteLine("hash1 = " + hash1);

// Or hash a file..
string hash2 = crypt.HashFileENC("qa_data/hamlet.xml");
Debug.WriteLine("hash2 = " + hash2);

// (The Crypt2 API provides many other ways to hash data..)

// -----------------------------------------------------------
// An ECDSA private key is used for signing.  The public key is for signature verification.
// Load our ECC private key.
// Our private key file contains this:

// 	// -----BEGIN PRIVATE KEY-----
// 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
// 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
// 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
// 	-----END PRIVATE KEY-----

Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
bool success = privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem");
if (success != true) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

// We'll need a PRNG source for random number generation.
// Use Chilkat's PRNG (for the Fortuna PRNG algorithm).
Chilkat.Prng prng = new Chilkat.Prng();

// Sign the hash..
Chilkat.Ecc ecdsa = new Chilkat.Ecc();
string ecdsaSigBase64 = ecdsa.SignHashENC(hash1,"base64",privKey,prng);
if (ecdsa.LastMethodSuccess != true) {
    Debug.WriteLine(ecdsa.LastErrorText);
    return;
}

Debug.WriteLine("ECDSA signature = " + ecdsaSigBase64);

// -----------------------------------------------------------
// Now let's verify the signature using the public key.

Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
success = pubKey.LoadFromFile("qa_data/ecc/secp256r1-pubkey.pem");
if (success != true) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

int result = ecdsa.VerifyHashENC(hash1,ecdsaSigBase64,"base64",pubKey);
if (result == 1) {
    Debug.WriteLine("Signature is valid.");
    return;
}

if (result == 0) {
    Debug.WriteLine("Signature is invalid.");
    return;
}

if (result < 0) {
    Debug.WriteLine(ecdsa.LastErrorText);
    Debug.WriteLine("The VerifyHashENC method call failed.");
    return;
}