I have the private key stored as .key file..

-----BEGIN RSA PRIVATE KEY-----
MIICXAIBAAKBgQD5YBS6V3APdgqaWAkijIUHRK4KQ6eChSaRWaw9L/4u8o3T1s8J
rUFHQhcIo5LPaQ4BrIuzHS8yzZf0m3viCTdZAiDn1ZjC2koquJ53rfDzqYxZFrId
7a4QYUCvM0gqx5nQ+lw1KoY/CDAoZN+sO7IJ4WkMg5XbgTWlSLBeBg0gMwIDAQAB
AoGASKDKCKdUlLwtRFxldLF2QPKouYaQr7u1ytlSB5QFtIih89N5Avl5rJY7/SEe
rdeL48LsAON8DpDAM9Zg0ykZ+/gsYI/C8b5Ch3QVgU9m50j9q8pVT04EOCYmsFi0
DBnwNBRLDESvm1p6NqKEc7zO9zjABgBvwL+loEVa1JFcp5ECQQD9/sekGTzzvKa5
SSVQOZmbwttPBjD44KRKi6LC7rQahM1PDqmCwPFgMVpRZL6dViBzYyWeWxN08Fuv
p+sIwwLrAkEA+1f3VnSgIduzF9McMfZoNIkkZongcDAzjQ8sIHXwwTklkZcCqn69
qTVPmhyEDA/dJeAK3GhalcSqOFRFEC812QJAXStgQCmh2iaRYdYbAdqfJivMFqjG
vgRpP48JHUhCeJfOV/mg5H2yDP8Nil3SLhSxwqHT4sq10Gd6umx2IrimEQJAFNA1
ACjKNeOOkhN+SzjfajJNHFyghEnJiw3NlqaNmEKWNNcvdlTmecObYuSnnqQVqRRD
cfsGPU661c1MpslyCQJBAPqN0VXRMwfU29a3Ve0TF4Aiu1iq88aIPHsT3GKVURpO
XNatMFINBW8ywN5euu8oYaeeKdrVSMW415a5+XEzEBY=
-----END RSA PRIVATE KEY-----

And i extracted public key from ssl certificate file..

Below is the code i tried to verify if private key matches with ssl certificate or not..

I used the modulus[i.e. private key get modulus==public key get modulus] to check if they are matching..

And this seems to hold only for RSAKEYS..

But i want to check for other keys as well..

Is there any other alternative to do the same..??

  private static boolean verifySignature(File serverCertificateFile, File serverCertificateKey) {
    try {
        byte[] certificateBytes = FileUtils.readFileToByteArray(serverCertificateFile);
        //byte[] keyBytes = FileUtils.readFileToByteArray(serverCertificateKey);
        RandomAccessFile raf = new RandomAccessFile(serverCertificateKey, "r");
        byte[] buf = new byte[(int) raf.length()];
        raf.readFully(buf);
        raf.close();
        PKCS8EncodedKeySpec kspec = new PKCS8EncodedKeySpec(buf);
        KeyFactory kf;
        try {
            kf = KeyFactory.getInstance("RSA");

            RSAPrivateKey privKey = (RSAPrivateKey) kf.generatePrivate(kspec);


            CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
            InputStream in = new ByteArrayInputStream(certificateBytes);
            //Generate Certificate in X509 Format
            X509Certificate cert = (X509Certificate) certFactory.generateCertificate(in);
            RSAPublicKey publicKey = (RSAPublicKey) cert.getPublicKey();

            in.close();
            return privKey.getModulus() == publicKey.getModulus();

        } catch (NoSuchAlgorithmException ex) {
            logger.log(Level.SEVERE, "Such algorithm is not found", ex);
        }  catch (CertificateException ex) {
            logger.log(Level.SEVERE, "certificate exception", ex);
        } catch (InvalidKeySpecException ex) {
            Logger.getLogger(CertificateConversion.class.getName()).log(Level.SEVERE, null, ex);
        }

    } catch (IOException ex) {
        logger.log(Level.SEVERE, "Signature verification failed.. This could be because the file is in use", ex);
    }
    return false;
}

And the code isn't working either.. throws invalidkeyspec exception