Unable to Decrypt the data properly using javax.crypto class and SunJCE

Question

Hello all,
I am not new to Java but new to this forums
but and JCE and i wanted to write a program that Encrypts a file and also another program that decrypts it. As far Encryption is concerned i have been successful but When it comes to Decryption things aren't looking bright i have some or the other Problem with it. plz help me out .
Here is the Code for my Programs
Encryption
Code:
import java.io.*;
import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import java.security.*;
import javax.swing.*;
class MyJCE
public static void main(String args[])throws Exception
Provider sunjce = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunjce);
JFileChooser jfc = new JFileChooser();
int selection= jfc.showOpenDialog(null);
if(selection==JFileChooser.APPROVE_OPTION)
FileInputStream fis = new FileInputStream(jfc.getSelectedFile());
System.out.println("Selected file " + jfc.getSelectedFile());
try{
KeyGenerator kg = KeyGenerator.getInstance("DESede");
SecretKey key= kg.generateKey();
byte[] mkey=key.getEncoded();
System.out.println(key);
SecretKeySpec skey = new SecretKeySpec(mkey, "DESede");
Cipher cipher=Cipher.getInstance("DESede/ECB/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE,skey);
byte[] data= new byte[fis.available()];
//reading the file into data byte array
byte[] result= cipher.update(data);
byte[] enc= new byte [fis.read(result)];
System.out.println("Encrypted =" + result);
File fi= new File("/home/srikar/Encrypted");
FileOutputStream fos= new FileOutputStream(fi);
fos.write(enc);
fos.close();
byte[] encodedSpeckey = skey.getEncoded();
FileOutputStream ks= new FileOutputStream("./key.txt");
ks.write(encodedSpeckey);
System.out.println("Key written to a file");
}//try
catch(Exception ex)
ex.printStackTrace();
}//catch
}This Creates a Encrypted File. and a Encrypted key.txt
Code:
import java.io.*;
import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import java.security.*;
import javax.swing.*;
class Decrypt
public static void main(String[] args)
try
JFileChooser jfc = new JFileChooser();
int selection= jfc.showOpenDialog(null);
if(selection==JFileChooser.APPROVE_OPTION)
FileInputStream fis = new FileInputStream(jfc.getSelectedFile());
System.out.println("Selected file " + jfc.getSelectedFile());
//Read from the Encrypted Data
int ll= (int)jfc.getSelectedFile().length();
byte[] buffer = new byte[ll];
int bytesRead=fis.read(buffer);
byte[] data= new byte[bytesRead];
System.arraycopy(buffer,0,data,0,bytesRead);
//Read the Cipher Settings
FileInputStream rkey= new FileInputStream("./key.txt");
bytesRead = rkey.read(buffer);
byte[] encodedKeySpec=new byte[bytesRead];
System.arraycopy(buffer,0,encodedKeySpec,0,bytesRead);
//Recreate the Secret Symmetric Key
SecretKeySpec skeySpec= new SecretKeySpec(encodedKeySpec,"DESede");
//create the cipher for Decrypting
Cipher cipher = Cipher.getInstance("DESede/ECB/NoPadding");
cipher.init(Cipher.DECRYPT_MODE,skeySpec);
byte[] decrypted= cipher.update(data);
FileOutputStream fos= new FileOutputStream("/home/srikar/Decrypted");
fos.write(decrypted);
}//if
}//try
catch(Exception e)
e.printStackTrace();
}//catch
}//main
}//classthis Decrypt.java is expected to decrypt the above encrypted file but this simply creates a plaintext file of the same size as the Encrypted file but its contents are unreadable.
Or I endup with Exceptions like BadPadding or IllegalBlockSize Exception if i use any other Algorithm .
Please help out
thanx in advance

Answer 1

Srikar2871 wrote:
Well thanx for ur reply but
As i said there are No issues with ENCRYPTION and am getting an Encrypted file exactly of the same size as that of the original file and NOT as null bytes and Even am able to get a Decrypted file of again the same size of the Encrypted File but this time that data inside is in unreadable format.I ran your code EXACTLY* as posted and the contents of the file when viewed in a Hex editor was
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00So unless you are running different code to what you have posted, your file will look the same.
Cheers,
Shane