Displaying an encrypted byte array of an image in android

Question

I have an image which I turn into a byte array. I then encrypt this byte array with AES and I want a visual result to display representing this encryption.

The problem is all the header and meta information is also encrypted so this encrypted byte array, which is passed to byteToImage(), is not recognized as a valid representation of an image i.e. decodeByteArray() returns null.

I have tried cutting off the first 512 bytes of the original image and appending that back on to the start of the encrypted byte array in the hope that this will restore the header information - but it hasn't worked. I have this with .png and .bmp images. What I ideally want is a way to represent a RAW image in android and encrypt this information byte for byte - leaving out the need to fiddle around with headers etc.

I would really appreciate any help.

private static byte[] imageToBytes(ImageView iv){

byte[] imageInByte = null;
Bitmap originalImage;
ByteArrayOutputStream baos = new ByteArrayOutputStream();

BitmapDrawable drawable = (BitmapDrawable) iv.getDrawable();

originalImage = drawable.getBitmap();

originalImage.compress(Bitmap.CompressFormat.PNG, 0, baos); // was 70
imageInByte = baos.toByteArray();

return imageInByte;

}

private static Bitmap bytesToImage(byte data[]) {


    // byte[] x = Base64.decode(data, Base64.DEFAULT); using x in place of data also fails
    Bitmap bmp = BitmapFactory.decodeByteArray(data, 0, data.length);

    return bmp;
}

Answer 1

Your idea will not work. If you encrypt just a lot of bytes of a bitmap byte array you will demolish its structure and after that you don't have a bitmap anymore. So you cannot display it. If you want to be able to display the 'encrypted' image then do it pixel wise. Have a look at Bitmap.getPixel()/setPixel() or Bitmap.getPixels()/setPixels().