decrypting with DES throws an ”InvalidKeyException: Parameters missing” when using other mode than ECB

Question

I basically use the code from here http://www.avajava.com/tutorials/lessons/how-do-i-encrypt-and-decrypt-files-using-des.html for an encryption app but I want to be able to chose the mode of operation so I added this:

private String key;
private static String algorithmMode;

    public DESCrypt(String password, String algorithmMode) {
        this.key = password;
        this.algorithmMode = "DES/" + algorithmMode + "/PKCS5Padding";
    }

the main looks like this:

public static void main(String[] args) {
        try {
            DESCrypt des = new DESCrypt("12345678", algorithmMode);

            // FileInputStream fis1 = new FileInputStream("d:\\_test.txt");
            // FileOutputStream fos1 = new FileOutputStream("d:\\_test.txt.des");
            // des.encrypt(fis1, fos1);

            FileInputStream fis = new FileInputStream("d:\\_test.txt.des");
            FileOutputStream fos = new FileOutputStream("d:\\_test.txt");
            des.decrypt(fis, fos);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

As I was saying in the title it works fine with ECB but with other modes I can only encrypt.

Answer 1

You are missing an IV value for your decryption. You need to include this in your Cipher.init call:

... Cipher.init(Cipher.DECRYPT, someKey, new IvParameterSpec(eightByteValue));

If you omit it from your encryption code, a random IV value will be generated. You will need to store this (retrieved via Cipher.getIV()) to use in your decryption code.