(C# UWP/WinRT) 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.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

// 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 = await crypt.HashFileENCAsync("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;
}