package sheet02.a2;

import java.security.KeyFactory;
import java.security.Signature;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class VerifyECDSA {
    public static void main(String[] args) throws Exception {
        if (args.length < 3) {
            System.out.println(
                    "Please specify in the following order: Public Key (X509), Signature (Base64), Message (plain text)");
            return;
        }

        final String PUBLIC_KEY = args[0];
        final String SIGNATURE = args[1];
        final String MESSAGE = args[2];

        final var kf = KeyFactory.getInstance("EC");
        final var pub = kf.generatePublic(new X509EncodedKeySpec(Base64.getDecoder().decode(PUBLIC_KEY)));

        final var sig = Signature.getInstance("SHA256withECDSA");
        sig.initVerify(pub);
        sig.update(MESSAGE.getBytes());
        System.out.println("Correct: " + sig.verify(Base64.getDecoder().decode(SIGNATURE)));
    }
}