Review

class Util {
   /**
    * Derives the ENC or MAC key from the keySeed.
    *
    * @param keySeed the key seed.
    * @param mode either <code>ENC_MODE</code> or <code>MAC_MODE</code>.
    * 
    * @return the key.
    */
   public static SecretKey deriveKey(byte[] keySeed, int mode)
   throws GeneralSecurityException {
      MessageDigest shaDigest = MessageDigest.getInstance("SHA1");
      shaDigest.update(keySeed);
      byte[] c = { 0x00, 0x00, 0x00, (byte)mode };
      shaDigest.update(c);
      byte[] hash = shaDigest.digest();
      byte[] key = new byte[24];
      System.arraycopy(hash, 0, key, 0, 8);
      System.arraycopy(hash, 8, key, 8, 8);
      System.arraycopy(hash, 0, key, 16, 8);
      SecretKeyFactory desKeyFactory = SecretKeyFactory.getInstance("DESede");
      return desKeyFactory.generateSecret(new DESedeKeySpec(key));
   }

}