Generating a user-specified key to encrypt

[whodaman]

Hi all, i'm trying to encrypt and decript a file using a user specified key. I managed to generate a random key using keygenerator. But how do I encrypt a file using a user specified passphrase?

Also, is it possible to encrypt objects instead of simply encripting a file?

Here's my code:

thank you in advance.

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



public class endecrypt implements Serializable{


    
    public static void main(String argv[]) throws Exception {       //main function

        FileInputStream fis;  //file to be encrypted
        FileOutputStream fos; //encrypted file                                         
        CipherOutputStream cos; // cipher to encrypt file


        //generate key with DES algorithim

        KeyGenerator keygen = KeyGenerator.getInstance("DES");
        SecretKey desKey = keygen.generateKey();


        //Cipher
        Cipher desCipher;                        

        // Create the cipher 
        desCipher = Cipher.getInstance("DES");

        // Initialize the cipher for encryption
        desCipher.init(Cipher.ENCRYPT_MODE, desKey);


        //Encryption
        fis = new FileInputStream("STUDENTDATA.txt"); // bring in the file to be
 encrypted
        fos = new FileOutputStream("ENSTUDENTDATA.txt");
        cos = new CipherOutputStream(fos, desCipher);
        byte[] b = new byte[8];
        int i = fis.read(b);
        while (i != -1) {
            cos.write(b, 0, i);
            i = fis.read(b);
        }
        cos.flush();
        System.out.println("Encrypted file!!!");

                           

        // Create the cipher 
        desCipher = Cipher.getInstance("DES");

        // Initialize the cipher for encryption
        desCipher.init(Cipher.DECRYPT_MODE, desKey);

        //Decrypt
        fis = new FileInputStream("ENSTUDENTDATA.txt"); // bring in the file to be encrypted
        fos = new FileOutputStream("DYSTUDENTDATA.txt");
        cos = new CipherOutputStream(fos, desCipher);
        b = new byte[8];
        i = fis.read(b);
        while (i != -1) {
            cos.write(b, 0, i);
            i = fis.read(b);
        }
        cos.flush();
        System.out.println("Decrypted File!!!");
    }
    
}

 

[sivajankan]

Hi
Following codes may helpfull to u to generate user defined key..

String keystring = "userdefinedstring";
byte[] k = keystring.getBytes();
Secretkey deskey = new SecretkeySpec(k, "DES"


With Regards
Siva


:

 

[whodaman]

Thank you for your help. But I seem to still run into problems when I try set up the Cipher with the "userdefinedstring". I get an

InvalidKeyException

.

String keystring = "userdefinedstring";
byte[] k = keystring.getBytes();
SecretKey desKey = new SecretKeySpec(k, "DES");

Cipher desCipher;
desCipher = Cipher.getInstance("DES");
desCipher.init(Cipher.ENCRYPT_MODE, desKey);