package sheet02.a2;

import java.nio.file.Files;
import java.nio.file.Path;
import java.security.KeyPairGenerator;
import java.security.Signature;
import java.util.Base64;

public class SignECDSA {
    public static void main(String[] args) throws Exception {
        final var gen = KeyPairGenerator.getInstance("EC");
        final var kp = gen.genKeyPair();

        final var bytes = Files.readAllBytes(Path.of("plaintext.txt"));
        final var sig = Signature.getInstance("SHA256withECDSA");
        sig.initVerify(kp.getPublic());
        sig.initSign(kp.getPrivate());
        sig.update(bytes);
        final var signature = sig.sign();

        Files.write(Path.of("signature.txt"), Base64.getEncoder().encode(signature));
        Files.write(Path.of("sign-key.pub"), Base64.getEncoder().encode(kp.getPublic().getEncoded()));
        Files.write(Path.of("sign-key"), Base64.getEncoder().encode(kp.getPrivate().getEncoded()));
    }
}