How to verify if the private key matches with the certificate..?

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

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

Solution

So, what's the problem with pairwise parameter checking?

If certificate specifies public key of type “RSA”, then:
1. Extract n, e from key file.
2. Compare these values with those in certificate.
If certificate specifies public key of type “DSA”, then:
1. Extract p, q, g, y from key file.
2. Compare these values with those in certificate.
If certificate specifies public key of type “blah-blah”, then:
1. Extract corresponding values from key file.
2. Compare these values with those in certificate.

And so on, i. e. each algorithm requires its own proper handling. No general algorithm may exist, provided that key file format is actually custom. However, you may still slightly generalize it by specifying value indexes only:

ComparisonScheme = new Dictionary<String, Integer[2][]> {
    { "RSA", {{0, 0}, {1, 1}} },
    { "DSA", {{0, 1}, {1, 2}, {2, 3}, {3, 0}} },
}

This is just an illustration, of course, — don't get syntax and numbers seriously.