Java self signed certificate and keystore usage

Question

I need to create public and private key along public certificate. I am able to generate the self sign certificate using the following code ...

    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");  
    keyPairGenerator.initialize(1024);  
    KeyPair KPair = keyPairGenerator.generateKeyPair(); 
   PrivateKey privkey = KPair.getPrivate();

  X509CertInfo info = new X509CertInfo();
  Date from = new Date();
  Date to = new Date(from.getTime() + days * 86400000l);
  CertificateValidity interval = new CertificateValidity(from, to);
  BigInteger sn = new BigInteger(64, new SecureRandom());
  X500Name owner = new X500Name(dn);

  info.set(X509CertInfo.VALIDITY, interval);
  info.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber(sn));
  info.set(X509CertInfo.SUBJECT, new CertificateSubjectName(owner));
  info.set(X509CertInfo.ISSUER, new CertificateIssuerName(owner));
  info.set(X509CertInfo.KEY, new CertificateX509Key(pair.getPublic()));
  info.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3));
  AlgorithmId algo = new AlgorithmId(AlgorithmId.md5WithRSAEncryption_oid);
  info.set(X509CertInfo.ALGORITHM_ID, new CertificateAlgorithmId(algo));

  // Sign the cert to identify the algorithm that's used.
  X509CertImpl cert = new X509CertImpl(info);
  cert.sign(privkey, algorithm);

  // Update the algorith, and resign.
  algo = (AlgorithmId)cert.get(X509CertImpl.SIG_ALG);
  info.set(CertificateAlgorithmId.NAME + "." + CertificateAlgorithmId.ALGORITHM, algo);
  cert = new X509CertImpl(info);
  cert.sign(privkey, algorithm);

Now i need to save the private and public key either by using keystore or any otherway so that i can retrieve those for signing any file or object. I tried using simple file streaming but it gave me error and seems like its not the proper way. Kindly guide me what should i do next. I want to use certificate and private key to sign some data and i want to save them so that i can use verification anytime.

Answer 1

i found the answer

   private  void savePublicKeyToFile(String fileName,
                                BigInteger mod, BigInteger exp) throws IOException {
     ObjectOutputStream oout = new ObjectOutputStream(
             new BufferedOutputStream(new FileOutputStream(fileName)));
     try {
         oout.writeObject(mod);
         oout.writeObject(exp);
     } catch (Exception e) {
        // throw new SomeException(e);
     } finally {
         oout.close();
     }
 }

  private  void savePrivteKeyToFile(String fileName,
                                BigInteger mod, BigInteger PublicExponent, BigInteger PrivateExponent,
            BigInteger PrimeP, BigInteger PrimeQ,BigInteger PrimeExponentP,BigInteger PrimeExponentQ,
            BigInteger CrtCoefficient) throws IOException {
     ObjectOutputStream oout = new ObjectOutputStream(
             new BufferedOutputStream(new FileOutputStream(fileName)));
     try {
         oout.writeObject(mod);
         oout.writeObject(PublicExponent);
         oout.writeObject(PrivateExponent);
         oout.writeObject(PrimeP);
         oout.writeObject(PrimeQ);
         oout.writeObject(PrimeExponentP);
         oout.writeObject(PrimeExponentQ);
         oout.writeObject(CrtCoefficient);
     } catch (Exception e) {
        // throw new SomeException(e);
     } finally {
         oout.close();
     }
 }


     // To save in keystore here is the way


     Certificate [] certChain = new Certificate[1];
    certChain[0] = ca;
    String strAlias = "abcalias", strPassword="mypass";
    KeyStore keyStore = KeyStore.getInstance("jks");
    keyStore.load(null,strPassword.toCharArray());
    keyStore.setEntry(strAlias,
       new KeyStore.PrivateKeyEntry((PrivateKey) KPair.getPrivate(), certChain),
       new KeyStore.PasswordProtection(strPassword.toCharArray()));

    FileOutputStream fkey = new FileOutputStream(strFilePath+".keystore"); 
    keyStore.store(fkey, strPassword.toCharArray());
    fkey.close();