Data missing when implementing 3DES using DES

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echipbk

Topic subject: Data missing when implementing 3DES using DES

Posted: Sun Mar 28, 2010 3:16 pm

Joined: Sun Mar 28, 2010 3:08 pm
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Here is the code:

Code:

import java.io.*;
import java.security.*;
import javax.crypto.*;

public class test {

    public static void main(String[] args) throws Exception
    {
        KeyGenerator keyg = KeyGenerator.getInstance("DES");
    SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
    keyg.init(56, random);

    SecretKey sk1 = keyg.generateKey();
        SecretKey sk2 = keyg.generateKey();

        Cipher cp1 = Cipher.getInstance("DES");
    cp1.init(Cipher.ENCRYPT_MODE, sk1);

        Cipher cp2 = Cipher.getInstance("DES");
        cp2.init(Cipher.DECRYPT_MODE, sk2);

        Cipher cp3 = Cipher.getInstance("DES");
        cp3.init(Cipher.ENCRYPT_MODE, sk1);

        FileInputStream fis = new FileInputStream("input.txt");
        FileOutputStream fos = new FileOutputStream("encrypted.txt");

        CipherOutputStream cos1 = new CipherOutputStream(fos, cp1);
        CipherOutputStream cos2 = new CipherOutputStream(cos1, cp2);
        CipherOutputStream cos3 = new CipherOutputStream(cos2, cp3);

        byte b[] = new byte[8];
        int i = fis.read(b);
        while(i != -1){
            cos3.write(b, 0, i);
            i = fis.read(b);
        }

        fis.close();
        cos3.close();

        //Decrypt contents from file
        FileInputStream fiss = new FileInputStream("encrypted.txt");
        FileOutputStream foss = new FileOutputStream("original.txt");
        cp1.init(Cipher.DECRYPT_MODE, sk1);
        cp2.init(Cipher.ENCRYPT_MODE, sk2);
        cp3.init(Cipher.DECRYPT_MODE, sk1);

        CipherInputStream cis1 = new CipherInputStream(fiss, cp1);
        CipherInputStream cis2 = new CipherInputStream(cis1, cp2);
        CipherInputStream cis3 = new CipherInputStream(cis2, cp3);

        i = cis3.read(b);
        while(i != -1){
            foss.write(b, 0, i);
            i = cis3.read(b);
        }

        cis3.close();
        foss.close();
    }
}
 

And this is the input.txt file:
This is the content of the message. Let's see what happen at the end

When I run this code, the original file is:
This is the content of the message. Let's see what happen at the

-> So the "end" word is missing. I don't know what has happened.

But when the input.txt file is:
This is the content of the message. Let's see what happen at the

Then the original.txt file is:
This is the content of the message. Let's see what happen at the

This time it works.

Can anyone show me why this happened ?? Thanks a lot.

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