Java DES

[xtingy]

Hellos.

Am having difficulty solving my problem as follows:

Im trying to write a program to perform DES encryption. I do not wish to generate a DES key using the SecretKey method as i have my own set of keys. I have the following:

plainText (8 bytes) in hex representation.
key(7 bytes) in hex representation.
Both are stored in the form of byte arrays.
Then i do a hex2Byte conversion for both plainText and key.
and i passed these 2 variables into my try block as shown below. Is it correct?

Nothing is displayed after i execute the program. Pls help! Thanks :)

try         
{                           
byte[] cipherText = null;                          
//init cipher             
KeySpec ks = new DESKeySpec(key);             
SecretKeyFactory kf =SecretKeyFactory.getInstance("DES"); 
SecretKey ky = kf.generateSecret(ks);             
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");             cipher.init(Cipher.ENCRYPT_MODE, ky);     
 
//encrypt             
cipherText = cipher.doFinal(plainText); 
System.out.println("Key: " +key); 
System.out.println("PlainText:"+plainText);         
 
//display cipherText             
System.out.println("CipherText: " + byte2Hex(cipherText));                      
}     
 
catch (Exception e)         {}
 

[cordeo]

Hellos.

Nothing is displayed after i execute the program. Pls help! Thanks :)

try         
{                           
byte[] cipherText = null;                          
//init cipher             
KeySpec ks = new DESKeySpec(key);             
SecretKeyFactory kf =SecretKeyFactory.getInstance("DES"); 
SecretKey ky = kf.generateSecret(ks);             
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");             cipher.init(Cipher.ENCRYPT_MODE, ky);     
 
//encrypt             
cipherText = cipher.doFinal(plainText); 
System.out.println("Key: " +key); 
System.out.println("PlainText:"+plainText);         
 
//display cipherText             
System.out.println("CipherText: " + byte2Hex(cipherText));                      
}     
 
catch (Exception e)         {}
 

I don't have time to put up a full answer at this very moment but as a programming rule: NEVER ignore exceptions by using an empty catch-block.

It's an often seen beginners mistake, but problems that otherwise would be reported might silently disappear, which is undesired of course. So write:

catch (Exception e) { e.printStackTrace(); }
 

and have a look at your console. Not being sure whether this is enhough help, it is an important step in the right direction.

[cordeo]

as a second rule,
2. Catch specific exceptions
By catching (java.lang.)Exception, you also catch things like IndexOutOfBoundsException, NegativeArraySizeException, NoSuchElementException, IOException and others that have nothing to do (at least, not directly) with the code in the try-block. Especially in the case of an empty catch-block, lots of problems that are neatly reported by java are silently ignored, causing

Nothing is displayed after i execute the program.

For example, you might have a wrong key size causing a InvalidKeyException:
java.security.InvalidKeyException: Wrong key size
at javax.crypto.spec.DESKeySpec.<init>(DashoA13*..)
at javax.crypto.spec.DESKeySpec.<init>(DashoA13*..)
at etc.

If plainText is null, you get
Exception in thread "main" java.lang.IllegalArgumentException: Null input buffer
at javax.crypto.Cipher.doFinal(DashoA13*..)
at etc.

        try {
            // making this null causes an IllegalArgumentException
            byte[] plainText = new byte[]{0x38,0x39};
            // making this shorter causes an InvalidKeyException
            byte[] key = new byte[]{0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37};
            byte[] cipherText = null;
            //init cipher      
            KeySpec ks = new DESKeySpec(key);
            SecretKeyFactory kf = SecretKeyFactory.getInstance("DES");
            SecretKey ky = kf.generateSecret(ks);
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, ky);
            //encrypt      
            cipherText = cipher.doFinal(plainText);
            System.out.println("Key: " + new String(key));
            System.out.println("PlainText:" + new String(plainText));
            //display cipherText          
            System.out.println("CipherText: " + byte2Hex(cipherText));
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (InvalidKeySpecException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        }
 

3. System.out.println for byte[]
This actually prints a java object pointer on the console:
System.out.println("Key: " + key);
for example might print
Key: [B@c7e553
Using a special routine like byte2Hex is a solution, otherwise, you might use

System.out.println("Key: " + new String(key));

as a quick workaround.