Question

I am running a java string encryption/decryption class that i got from the internet! Here is the class with little modification :

public class EncrypterDecrypter
{
Cipher ecipher;
Cipher dcipher;

EncrypterDecrypter(SecretKey key)
{
    try {
        ecipher = Cipher.getInstance("DES");
        dcipher = Cipher.getInstance("DES");
        ecipher.init(Cipher.ENCRYPT_MODE, key);
        dcipher.init(Cipher.DECRYPT_MODE, key);

    } catch (javax.crypto.NoSuchPaddingException e) {
    } catch (java.security.NoSuchAlgorithmException e) {
    } catch (java.security.InvalidKeyException e) {
    }
}   

}

public class EncryptionTester
{

public static void main(String[] args)
{
    try
    {
        //Generate a temporary key.
        SecretKey key = KeyGenerator.getInstance("DES").generateKey();

        //Create Encrypter/Decrypter class
        EncrypterDecrypter crypto = new EncrypterDecrypter(key);

        //More lines of code to use crypto object
    }
     catch (Exception e)
     {
     } 
}

}

My problem is that each time i create an new instance of EncrypterDecrypter class i get differents encrypted string yet the string to encrypt is still the same! My mind tells me that the problem would be the SecretKey object which keeps changing each time there is a new instance created, i would like to know how i can make the SecretKey object the same for all instances of Encrypter/Decrypter Class if that be the cause of the problem!

Answer 1

If you used the javax.crypto package, then the encrypt and decryp methods look okay.
Try to generate your key like that:

final SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
final SecretKey key = skf.generateSecret(new DESKeySpec(new byte [] {/*The key*/}));
instance.EncrypterDecrypter(key);                     //Initialization of your Cipher objects
String encrypted = instance.encrypt("This is a test");
System.out.println(instance.decrypt(encrypted));      //"This is a test"

You should do something in the catches.