public String getD() {
        return d;
    }
@Test
    public void testPublicJWKCreation()
            throws InvalidAlgorithmParameterException,
                    NoSuchAlgorithmException,
                    NoSuchProviderException {
        KeyPair keyPair = Keys.createSecp256k1KeyPair();
        BCECPublicKey publicKey = (BCECPublicKey) keyPair.getPublic();
        Secp256k1JWK jwk = new Secp256k1JWK.Builder(publicKey).build();
        assertPublicJWK(jwk);
        assertNull(jwk.getD());
    }