//Java classes that are mandatory to import for encryption and decryption process   
import java.io.FileInputStream;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.OutputStream;  
import java.security.InvalidAlgorithmParameterException;  
import java.security.InvalidKeyException;  
import java.security.NoSuchAlgorithmException;  
import java.security.spec.AlgorithmParameterSpec;  
import javax.crypto.Cipher;  
import javax.crypto.CipherInputStream;  
import javax.crypto.CipherOutputStream;  
import javax.crypto.KeyGenerator;  
import javax.crypto.NoSuchPaddingException;  
import javax.crypto.SecretKey;  
import javax.crypto.spec.IvParameterSpec;   
public class DesProgram   
{  
//creating an instance of the Cipher class for encryption  
private static Cipher encrypt;  
//creating an instance of the Cipher class for decryption  
private static Cipher decrypt;  
//initializing vector  
private static final byte[] initialization_vector = { 22, 33, 11, 44, 55, 99, 66, 77 };  
//main() method  
public static void main(String[] args)   
{  
//path of the file that we want to encrypt  
String textFile = "C:/Users/Anubhav/Desktop/DemoData.txt";  
//path of the encrypted file that we get as output  
String encryptedData = "C:/Users/Anubhav/Desktop/encrypteddata.txt";  
//path of the decrypted file that we get as output  
String decryptedData = "C:/Users/Anubhav/Desktop/decrypteddata.txt";  
try   
{  
//generating keys by using the KeyGenerator class  
SecretKey scrtkey = KeyGenerator.getInstance("DES").generateKey();  
AlgorithmParameterSpec aps = new IvParameterSpec(initialization_vector);  
//setting encryption mode  
encrypt = Cipher.getInstance("DES/CBC/PKCS5Padding");  
encrypt.init(Cipher.ENCRYPT_MODE, scrtkey, aps);  
//setting decryption mode  
decrypt = Cipher.getInstance("DES/CBC/PKCS5Padding");  
decrypt.init(Cipher.DECRYPT_MODE, scrtkey, aps);  
//calling encrypt() method to encrypt the file  
encryption(new FileInputStream(textFile), new FileOutputStream(encryptedData));  
//calling decrypt() method to decrypt the file  
decryption(new FileInputStream(encryptedData), new FileOutputStream(decryptedData));  
//prints the stetment if the program runs successfully  
System.out.println("The encrypted and decrypted files have been created successfully.");  
}   
//catching multiple exceptions by using the | (or) operator in a single catch block  
catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | InvalidAlgorithmParameterException | IOException e)   
{  
//prints the message (if any) related to exceptions  
e.printStackTrace();  
}  
}  
//method for encryption  
private static void encryption(InputStream input, OutputStream output)  
throws IOException   
{  
output = new CipherOutputStream(output, encrypt);  
//calling the writeBytes() method to write the encrypted bytes to the file   
writeBytes(input, output);  
}   
//method for decryption  
private static void decryption(InputStream input, OutputStream output)  
throws IOException   
{  
input = new CipherInputStream(input, decrypt);  
//calling the writeBytes() method to write the decrypted bytes to the file    
writeBytes(input, output);  
}  
//method for writting bytes to the files   
private static void writeBytes(InputStream input, OutputStream output)  
throws IOException   
{  
byte[] writeBuffer = new byte[512];  
int readBytes = 0;  
while ((readBytes = input.read(writeBuffer)) >= 0)   
{  
output.write(writeBuffer, 0, readBytes);  
}  
//closing the output stream  
output.close();  
//closing the input stream  
input.close();  
}   
}