Help with some vb.net and java code- Help still needed

zekesonxx, on 01 April 2014 - 12:39 AM said:

This is actually just a really confusing implementation of ROT. Here's a direct JS port:

Bomb Bloke, on 01 April 2014 - 01:02 PM said:

Here's a stab at it; I've not tested it, as I've not played with Java for a little while and am curious as to whether I can still get something this simple right without the help of a compiler. ;)/>

Spoiler

public static string Decrypt(String text1, String key, boolean isEncrypt) {
	int j = -1;
	char[] textChar = text1.toCharArray(), keyChar = key.toCharArray();
	
	for (int i=0;i<keyChar.length;i++) if (keyChar[i] < 48 || keyChar[i] > 57) {
		System.out.println("Warning: Decrypt function called with invalid key.");
		return "";
	} else keyChar[i] -= 48;

	if (textChar.length > 0 &amp;&amp; keyChar.length > 0) {
		for (int i=0;i<textChar.length;i++) {
			j++;
			if (j == keyChar.length) j = 0;

			if (isEncrypt) {
				if (textChar[i] + keyChar[j] > 255) {
					textChar[i] += keyChar[j] - 255;
				} else {
					textChar[i] += keyChar[j];
				}
			} else {
				if (textChar[i] - keyChar[j] < 1) {
					textChar[i] -= keyChar[j] + 255;
				} else {
					textChar[i] -= keyChar[j];
				}
			}
		}
	} else {
		System.out.println("Warning: Decrypt function called with empty text.");
		return "";
	}

	return String.valueOf(textChar);
}

There may be some "loss of precision" errors lurking in there, but they should be easy to sort out if so.

Bomb Bloke, on 01 April 2014 - 10:36 PM said:

Indeed, that'd need to be switched to an upper-case S.

final EditText userinputET = (EditText) findViewById(R.id.txtin);
   final String in = userinputET.getText().toString();
   Button mbtn = (Button) findViewById(R.id.btn);
   //final Button btn = (Button) findViewById(R.id.btn);

   mbtn.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
	Context context = getApplicationContext();
	Toast toast = Toast.makeText(context ,in , 3);
	toast.show();
   }
  });

6677, on 01 April 2014 - 09:14 AM said:

zekesonxx, on 01 April 2014 - 12:39 AM said:

This is actually just a really confusing implementation of ROT. Here's a direct JS port:

Firstly he was after Java not javascript (the 2 contrary to name are not related).

And that is most certainly not ROT. Rot would shift all characters in a given string by n places, typically used with 13 on upper case only text. This shifts each character by the value of the corresponding character in the key with a modulo for where the values overflow. Closest I can think of from the top of my head that also does this is Solitaire but that also has some complexities of its own.
Problem with this is that if 2 messages are sent using the same key it does become a rather trivial operation to reverse engineer the key and from that the messages.

t h i s   w i l l   b e c o m e   r o t a t e d
4 3 5 4 3 5 4 3 5 4 3 5 4 3 5 4 3 5 4 3 5 4 3 5