Elliptic Curve with Digital Signature Algorithm (ECDSA) implementation on BouncyCastle

Question

I am trying to implement ECDSA (Elliptic Curve Digital Signature Algorithm) but I couldn't find any examples in Java which use Bouncy Castle. I created the keys, but I really don't know what kind of functions I should use to create a signature and verify it.

public static KeyPair GenerateKeys()
    throws NoSuchAlgorithmException, NoSuchProviderException, InvalidAlgorithmParameterException
{
    ECParameterSpec ecSpec = ECNamedCurveTable.getParameterSpec("B-571");
    KeyPairGenerator g = KeyPairGenerator.getInstance("ECDSA", "BC");
    g.initialize(ecSpec, new SecureRandom());
    return g.generateKeyPair();
}

Answer 1

owlstead is correct. And to elaborate a bit more, you can do this:

KeyPair pair = GenerateKeys();
Signature ecdsaSign = Signature.getInstance("SHA256withECDSA", "BC");
ecdsaSign.initSign(pair.getPrivate());
ecdsaSign.update(plaintext.getBytes("UTF-8"));
byte[] signature = ecdsaSign.sign();

And to verify:

Signature ecdsaVerify = Signature.getInstance("SHA256withECDSA", "BC");
ecdsaVerify.initVerify(pair.getPublic());
ecdsaVerify.update(plaintext.getBytes("UTF-8"));
boolean result = ecdsaVerify.verify(signature);

Answer 2

You seem to be using Bouncy Castle mainly as provider. In that case you could simply use Signature.getInstance("SHA256withECDSA", "BC").