How to insert my own key

Question

Hi,
i using the following code to encypt a string, but i now i need to encrypt using my own key, what i have to change in this code to make that possible...
String message="test";
KeyGenerator kgen = KeyGenerator.getInstance("Rijndael");
       kgen.init(128);
      SecretKey skey = kgen.generateKey();
       byte[] raw = skey.getEncoded();
       SecretKeySpec skeySpec = new SecretKeySpec(raw, "Rijndael");
        // Instantiate the cipher
       Cipher cipher = Cipher.getInstance("Rijndael");
       cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
       byte[] encrypted = cipher.doFinal((args.length == 0 ?message : args[0]).getBytes());

Answer 1

OK, try this:
import java.math.BigInteger;
byte[] raw = new
BigInteger("c9536544-9b54-4986-75a1-45982b69587c".repl
aceAll("-","")).toByteArray();
This does not really work. It tries to convert the key using base 10, not base 16, and it puts a leading zero in the byte array so produces a 17 byte key. See for example
        String hexKey = "c9536544-9b54-4986-75a1-45982b69587c".replaceAll("-","");
        System.out.println(hexKey.length() + "\t" + hexKey);
        byte[] raw = new BigInteger(hexKey, 16).toByteArray();       
        System.out.println(raw.length + "\t" + java .util.Arrays.toString(raw));In this case one could just remove the leading zero from the resulting 'raw' but this would then fail if using a key that has a genuine leading zero.
It would be better to use one of the free Hex decoders out there. I use 'jakarta commons codec'. Google will find it.