myCrypto

package rs.ac.uns.ftn.informatika.ib.crypto;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidParameterSpecException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;

import rs.ac.uns.ftn.informatika.ib.util.Base64;

public class MyCrypto {

    /**
     * @param args
     */
    private SecretKey secretKey;
    private byte []data;
    private BufferedWriter bw;

    public MyCrypto() {
        //Security.addProvider(new BouncyCastleProvider());
    }

    public void getByteFromFile() {
        try {
            data =Files.readAllBytes(Paths.get("C:\\Users\\Branislav\\Desktop\\bp2\\Uputstvo_za_Oracle_XE.txt"));
            System.out.println("length in bytes: "+ data.length);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private void generateKey() {
        try {
            //generator para kljuceva za DES algoritam
            KeyGenerator   keyGen = KeyGenerator.getInstance("AES");
            //generise kljuc za DES
            secretKey = keyGen.generateKey();

        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }


    public void saveKey(byte[] key) {

        try {
                /*bw= new BufferedWriter(new FileWriter("kljucevi.txt",true));
                bw.write(key.hashCode());
                bw.newLine();
                bw.close();*/


             File kekFile = new File("kljucevi.txt");
             FileOutputStream f = new FileOutputStream(kekFile);
             f.write(key);
             f.close();

        } catch (IOException e) {
            e.printStackTrace();

            }


    }

    private void transfer() {

        try {

            Cipher chipEnc = Cipher.getInstance("AES/CBC/PKCS5Padding");
            chipEnc.init(Cipher.ENCRYPT_MODE, secretKey);
            byte[] ciphertext = chipEnc.doFinal(data);
            System.out.println("Kriptovan text: " + Base64.encodeToString(ciphertext));

            saveKey(secretKey.getEncoded());

            //The basic purpose of an IV is to ensure
            //that the encryption function works differently every time
            //it adds an element of randomness, or at least unpredictability
            //to your ciphertexts.
            AlgorithmParameters params = chipEnc.getParameters();
            byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();



            Cipher chipDec = Cipher.getInstance("AES/CBC/PKCS5Padding");
            chipDec.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
            byte[] plainText = chipDec.doFinal(ciphertext);
            System.out.println("Primljeni text: " + new String(plainText));

        }
        catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (BadPaddingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvalidParameterSpecException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }


    public static void main(String[] args) {
        // TODO Auto-generated method stub
        MyCrypto c = new MyCrypto();
        //use symetric AES algorithm
        c.getByteFromFile();
        c.generateKey();
        c.transfer();

    }

}