Generate a self signed X509 certificate with Bouncy Castle

cert.java

//Generate a self signed X509 certificate with Bouncy Castle.
//        StringBuilder sb = new StringBuilder();
//        
//        for (int i = 0; i < pub.length; ++i)
//        {
//            sb.append(Integer.toHexString(0x0100 + (pub[i] & 0x00FF)).substring(1));
//        }
//        
//        System.out.println(sb);
//        sb.setLength(0);
//        
//        for (int i = 0; i < pri.length; ++i)
//        {
//            sb.append(Integer.toHexString(0x0100 + (pri[i] & 0x00FF)).substring(1));
//        }
//        
//        byte[] enc = new PKCS8Generator(privateKey).generate().getContent();
//        
//        System.out.println(new String(Base64.encodeBase64(enc)));
//        
////        new JcaPKCS8Generator(privateKey, new Output)
//        
//        Cipher cipher = SecurityUtils.getCipher("RSA");
//        cipher.init(Cipher.DECRYPT_MODE, privateKey);
//        byte[] doFinal = cipher.doFinal(pub);
//        System.out.println(new String(doFinal));
//        
//        System.out.println(sb);


/**
     * Generate a self signed X509 certificate with Bouncy Castle.
     */
    static void generateSelfSignedX509Certificate() throws Exception {

        // yesterday
        Date validityBeginDate = new Date(System.currentTimeMillis() - 24 * 60 * 60 * 1000);
        // in 2 years
        Date validityEndDate = new Date(System.currentTimeMillis() + 2 * 365 * 24 * 60 * 60 * 1000);

        // GENERATE THE PUBLIC/PRIVATE RSA KEY PAIR
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC");
        keyPairGenerator.initialize(1024, new SecureRandom());

        java.security.KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // GENERATE THE X509 CERTIFICATE
        X509V1CertificateGenerator certGen = new X509V1CertificateGenerator();
        X500Principal dnName = new X500Principal("CN=John Doe");

        certGen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis()));
        certGen.setSubjectDN(dnName);
        certGen.setIssuerDN(dnName); // use the same
        certGen.setNotBefore(validityBeginDate);
        certGen.setNotAfter(validityEndDate);
        certGen.setPublicKey(keyPair.getPublic());
        certGen.setSignatureAlgorithm("SHA256WithRSAEncryption");

        X509Certificate cert = certGen.generate(keyPair.getPrivate(), "BC");

        // DUMP CERTIFICATE AND KEY PAIR

        System.out.println(Strings.repeat("=", 80));
        System.out.println("CERTIFICATE TO_STRING");
        System.out.println(Strings.repeat("=", 80));
        System.out.println();
        System.out.println(cert);
        System.out.println();

        System.out.println(Strings.repeat("=", 80));
        System.out.println("CERTIFICATE PEM (to store in a cert-johndoe.pem file)");
        System.out.println(Strings.repeat("=", 80));
        System.out.println();
        PEMWriter pemWriter = new PEMWriter(new PrintWriter(System.out));
        pemWriter.writeObject(cert);
        pemWriter.flush();
        System.out.println();

        System.out.println(Strings.repeat("=", 80));
        System.out.println("PRIVATE KEY PEM (to store in a priv-johndoe.pem file)");
        System.out.println(Strings.repeat("=", 80));
        System.out.println();
        pemWriter.writeObject(keyPair.getPrivate());
        pemWriter.flush();
        System.out.println();
    }

X509V1CertificateGenerator is now deprecated /-:

X509V1CertificateGenerator is now deprecated /-:

You should now use org.bouncycastle.cert.X509v3CertificateBuilder;