Standard Practice For Protecting Sensitive Data in Java Application

// Java Program Demonstrating How Can We Get Secured
// Random Numbers from SecureRandom class

// Importing required classes
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

// Main class
class GFG {

    // Main driver method
    public static void main(String[] args)
    {

        // Try block to check for exceptions
        try {

            // Initialize a secure random number generator
            SecureRandom secureRandom
                = SecureRandom.getInstance("SHA1PRNG");

            // Method 1
            // Calling nextBytes method to generate Random
            // Bytes
            byte[] bytes = new byte[512];
            secureRandom.nextBytes(bytes);

            // Printing the SecureRandom number by
            // calling secureRandom.nextDouble()
            System.out.println(
                " Secure Random # generated by calling nextBytes() is "
                + secureRandom.nextDouble());

            // Method 2
            // Using setSeed(byte[]) to reseed a Random
            // object
            int seedByteCount = 10;
            byte[] seed
                = secureRandom.generateSeed(seedByteCount);

            secureRandom.setSeed(seed);

            System.out.println(
                " Secure Random # generated using setSeed(byte[]) is  "
                + secureRandom.nextDouble());
        }

        // Catch block to handle the exceptions
        catch (NoSuchAlgorithmException noSuchAlgo) {
            // Display message if it occurs
            System.out.println(" No Such Algorithm exists "
                               + noSuchAlgo);
        }
    }
}

// Java Program to Illustrate AES Encryption

// Importing required classes
import java.io.*;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;

// Main class
class GFG {

    // Encryption function
    // function 1
    public static void encryptEcb(String filenamePlain,
                                  String filenameEnc,
                                  byte[] key)
        throws IOException, NoSuchAlgorithmException,
               NoSuchPaddingException, InvalidKeyException,
               IllegalBlockSizeException,
               BadPaddingException
    {

        // Creating cipher instance OF AES encryption
        Cipher cipher
            = Cipher.getInstance("AES/ECB/PKCS5PADDING");

        // Specifying the algorithm
        SecretKeySpec secretKeySpec
            = new SecretKeySpec(key, "AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);

        // Try block to check for exceptions
        try (FileInputStream fis
             = new FileInputStream(filenamePlain);

             // Creating objects of BufferedInputStream,
             // FileOutputStream and BufferedOutputStream
             BufferedInputStream inputstream
             = new BufferedInputStream(fis);
             FileOutputStream outputstream
             = new FileOutputStream(filenameEnc);
             BufferedOutputStream bufferedOutputStream
             = new BufferedOutputStream(outputstream)) {

            // Defining the buffer
            byte[] ibufffer = new byte[1024];

            int length;

            // Reading while read buffer has data
            while ((length = inputstream.read(ibufffer))
                   != -1) {

                // Creating cipher with buffer
                byte[] obuffer
                    = cipher.update(ibufffer, 0, length);

                if (obuffer != null)

                    // Writing encrypted text to buffer
                    bufferedOutputStream.write(obuffer);
            }

            byte[] obuffer = cipher.doFinal();

            if (obuffer != null)
                bufferedOutputStream.write(obuffer);
        }
    }

    // Method 3
    // Decryption method
    public static void decryptEcb(String filenameEnc,
                                  String filenameDec,
                                  byte[] key)
        throws IOException, NoSuchAlgorithmException,
               NoSuchPaddingException, InvalidKeyException,
               IllegalBlockSizeException,
               BadPaddingException
    {

        // Try block to check for exceptions
        try (FileInputStream inputStream
             = new FileInputStream(filenameEnc);
             FileOutputStream outputStream
             = new FileOutputStream(filenameDec)) {
            // Defining buffer
            byte[] ibuffer = new byte[1024];
            int length;

            // Creating cipher instance OF AES decryption
            Cipher cipher = Cipher.getInstance(
                "AES/ECB/PKCS5PADDING");
            SecretKeySpec secretKeySpec
                = new SecretKeySpec(key, "AES");
            cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);

            // While input stream not empty
            while ((length = inputStream.read(ibuffer))
                   != -1) {

                // Reading into the buffer
                byte[] obuffer
                    = cipher.update(ibuffer, 0, length);
                if (obuffer != null)

                    // Now writing to output buffer
                    outputStream.write(obuffer);
            }

            byte[] obuffer = cipher.doFinal();
            if (obuffer != null)
                outputStream.write(obuffer);
        }
    }

    // Method 3
    // Main driver method
    public static void main(String[] args)
        throws IOException, NoSuchPaddingException,
               NoSuchAlgorithmException, BadPaddingException
               ,
               IllegalBlockSizeException,
               InvalidKeyException
    {

        // Display message
        System.out.println("/****AES Encryption*******/");

        // Placing the PDF path
        String pFileName
            = "/home/aniket/IdeaProjects/Gfg Programs/MAD FINAL.pdf";
        String cFileName = "your pdf.enc";

        // Placing the PDF name
        String decFileName = "your pdf.pdf";

        // Creating cipher key 56 bit key length
        byte[] cipher_key
            = "12345678901234561234567890123456".getBytes(
                "UTF-8");
        encryptEcb(pFileName, cFileName, cipher_key);
        decryptEcb(cFileName, decFileName, cipher_key);

        // Print and display the file credentials
        System.out.println(
            "file of encryption: " + pFileName + "\n"
            + "created encrypted file  : " + cFileName
            + "\n"
            + "created decrypted file  : " + decFileName);
    }
}