Bitwise Operations on type byte vs byte[]

Question

Here is the bit of code I'm working with:

byte[] encodedBytes1 = null;
byte[] encodedBytes2 = null;
try {
    Cipher c = Cipher.getInstance(encryptationMode);
    c.init(Cipher.ENCRYPT_MODE, key);
    encodedBytes1 = c.doFinal(TestText1.getBytes());
    encodedBytes2 = c.doFinal(TestText2.getBytes());
} catch (Exception e) {
    //Log.e(TAG, "AES encryption error");
}
byte[] encodedHomo = null;
boolean encoded1_2 = TestText1.getBytes() || TestText2.getBytes();

So I'm trying to do bitwise operations on encodedBytes1 and encodedBytes2 and make that new value encodedHomo (my project is homomorphic encryption on AES algorithm). Why can't I perform bitwise operation operations on type byte[]? What is, if any, the difference between the type byte and byte[]?

One is a primitive and the other is an object containing an array of `bytes` They don't have any method or functionality in common. — Peter Lawrey, Apr 17 '16 at 18:08

Peter Lawrey · Answer 1 · 2016-04-17T18:15:50.297

1

If you want to do a bitwise OR between two byte arrays you need to do this for each byte.

public static byte[] bitwiseOr(byte[] bytes1, byte[] bytes2) {
    if (bytes1.length < bytes2.length)
       return bitwiseOr(bytes2, bytes1);
    // bytes1 is never shorter than bytes2
    byte[] ret = bytes1.clone();
    for (int i = 0; i < bytes2.length; i++)
        ret[i] |= bytes2[i];
    return ret;
}

Note: there is no || operation for two byte or two byte[] There is only | for two byte

edited Apr 17 '16 at 18:15

answered Apr 17 '16 at 18:10

Peter Lawrey

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With `&` I would take the `min` of the lengths too, but with `|` I would take the `max` and just copy the remainder of the longer array. – maraca Apr 17 '16 at 18:12
@maraca I have updated my answer to take the longer length. – Peter Lawrey Apr 17 '16 at 18:16

score -1 · Answer 2 · answered Apr 17 '16 at 18:10

-1

Bitwise operations work on primitive data types, an array is not a primitive data type.

The bitwise OR operation, for example, has a well defined behavior for numbers but not for compound objects (which are not simply 'made of bits').

answered Apr 17 '16 at 18:10

Jack

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score -1 · Answer 3 · answered Apr 17 '16 at 18:11

-1

Java ain't C. Your byte[] objects aren't pointers to lots of bits.

You have to do your bitwise ops on each byte in the byte[]s spearately.

answered Apr 17 '16 at 18:11

Bohemian

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You can't do that in C either. ;) – Peter Lawrey Apr 17 '16 at 18:17

Bitwise Operations on type byte vs byte[]

3 Answers3