Java string encrypt

Question

I am using the encryption class in Objective C for my iPhone app but I am struggling to get the same functionality working in JAVA from my android app. My encryption code is below:

NSString * _secret = @"password";
NSString * _key = @"1428324560542678";

StringEncryption *crypto = [[StringEncryption alloc] init];
NSData *_secretData = [_secret dataUsingEncoding:NSUTF8StringEncoding];
CCOptions padding = kCCOptionPKCS7Padding;
NSData *encryptedData = [crypto encrypt:_secretData key:[_key dataUsingEncoding:NSUTF8StringEncoding] padding:&padding];

I have tried to replicate it in JAVA but I get a different string when I encode the same data. So I am doing something wrong but I can't figure it out. Here is my JAVA code:

byte[] key = "1428324560542678".getBytes();

Cipher c = null;
            try {
                c = Cipher.getInstance("AES/ECB/PKCS7Padding");
            } catch (NoSuchAlgorithmException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

SecretKeySpec k =  new SecretKeySpec(key, "AES");
            try {
                c.init(Cipher.ENCRYPT_MODE, k);
            } catch (InvalidKeyException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

    try {
        EditText tv1passwordText = (EditText) findViewById(R.id.password);
        String password = URLEncoder.encode(tv1passwordText.getText().toString(), "UTF-8");

            byte[] encryptedData = c.doFinal( password.getBytes());

Can anyone see where I am going wrong?

Based on the comments below I added getBytes but the strings produced are still different:

byte[] key = null;
            try {
                key = "1428324560542678".getBytes("UTF-8");
            } catch (UnsupportedEncodingException e2) {
                // TODO Auto-generated catch block
                e2.printStackTrace();
            }

            Cipher c = null;
            try {
                c = Cipher.getInstance("AES/ECB/PKCS7Padding");
            } catch (NoSuchAlgorithmException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            SecretKeySpec k =  new SecretKeySpec(key, "AES");
            try {
                c.init(Cipher.ENCRYPT_MODE, k);
            } catch (InvalidKeyException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {
                EditText tv1passwordText = (EditText) findViewById(R.id.password);

                byte[] password = tv1passwordText.getText().toString().getBytes("UTF-8");

                byte[] encryptedData = c.doFinal(password);

You need to specify the character set in getBytes() if you want the strings to match. — Mel Nicholson
– Mel Nicholson, Commented Apr 11, 2013 at 15:26

Mgamerz · Accepted Answer · 2014-02-15 23:12:06Z

7

Here is a sample of encryption and decryption:

public static SecretKey generateKey() throws NoSuchAlgorithmException, InvalidKeySpecException {
    return secret = new SecretKeySpec(password.getBytes(), "AES");
}

public static byte[] encryptMsg(String message, SecretKey secret) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidParameterSpecException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException {
/* Encrypt the message. */
    Cipher cipher = null;
    cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    cipher.init(Cipher.ENCRYPT_MODE, secret);
    byte[] cipherText = cipher.doFinal(message.getBytes("UTF-8"));
    return cipherText;
}

public static String decryptMsg(byte[] cipherText, SecretKey secret) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidParameterSpecException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException {

    /* Decrypt the message, given derived encContentValues and initialization vector. */
    Cipher cipher = null;
    cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
   cipher.init(Cipher.DECRYPT_MODE, secret);
    String decryptString = new String(cipher.doFinal(cipherText), "UTF-8");
    return decryptString;
}

To encrypt:

    SecretKey secret = EncUtil.generateKey();
    EncUtil.encryptMsg(<String to Encrypt>, secret))

to decrypt

    EncUtil.decryptMsg(<byte[]>, secret))

edited Feb 15, 2014 at 23:12

Mgamerz

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answered Apr 11, 2013 at 16:51

wangyif2

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4 Comments

RyPope Over a year ago

@wangyif2 What class is EncUtil?

wangyif2 Over a year ago

@RyPope, It will be w/e class the encryptMsg method sits in (Completely up to you).

Mgamerz Over a year ago

If I'm not mistaken your code snippet assumes 'secret' is static too. If it's not you have to remove secret = in the generate method.

Jono Over a year ago

where do you get the secret key ffrom or how do u generate one?

Zim-Zam O'Pootertoot · Accepted Answer · 2013-04-11 15:25:42Z

0

Instead of using ECB, you ought to use CBC or CTR if possible. ECB is insecure.

It looks like your Objective-C code is using UTF-8 encoding, but you're not specifying this in your Java code. Use getBytes("UTF-8").

answered Apr 11, 2013 at 15:25

Zim-Zam O'Pootertoot

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1 Comment

user1661369 Over a year ago

Thanks for your help everyone. I hadn't used getBytes so I changed my code to use getBytes but still no luck.

Peter Elliott · Accepted Answer · 2013-04-11 15:26:49Z

0

One thing that I've noticed that has caused problems in the past is that the iOS string being encrypted is actually "Hello World\0", eg the string to be encrypted with an extra null at the end. so try adding a \0 to the end of your string in Java and see if it produces the same results.

Additionally, the URLEncoder step on java may be introducing extra control characters and other things that are not present on the iOS side. It may be worthwhile to compare the text after this with the text going into the iOS encryption step to ensure that they are exactly the same

answered Apr 11, 2013 at 15:26

Peter Elliott

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3 Comments

user1661369 Over a year ago

Removed the URL encoder and used the getBytes method as suggested but still no joy.

Peter Elliott Over a year ago

did you try adding a \0 to the end of the string you are getting from the password field?

user1661369 Over a year ago

No joy, I tried adding the \0 to the end of the string but the encoded string was still different

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