import javax.crypto.*;
import java.security.*;
import java.util.Arrays;

/** JEP 452 (final): Key Encapsulation Mechanism API, with the DHKEM implementation that ships in 21. */
public class KemDemo {
    public static void main(String[] args) throws Exception {
        KeyPairGenerator g = KeyPairGenerator.getInstance("X25519");
        KeyPair kp = g.generateKeyPair();
        KEM kem = KEM.getInstance("DHKEM");
        KEM.Encapsulator enc = kem.newEncapsulator(kp.getPublic());
        KEM.Encapsulated e = enc.encapsulate();
        SecretKey sender = e.key();
        SecretKey receiver = kem.newDecapsulator(kp.getPrivate()).decapsulate(e.encapsulation());
        System.out.println("algorithm       : " + kem.getAlgorithm());
        System.out.println("secrets equal   : " + Arrays.equals(sender.getEncoded(), receiver.getEncoded()));
        System.out.println("secret length   : " + sender.getEncoded().length + " bytes");
        System.out.println("ciphertext length: " + e.encapsulation().length + " bytes");
    }
}