Self Encryption in Java

Question

I am writing a program for a class to first encrypt a string with a given key. This part is completed. The next part is where I have a problem or not a problem in itself. it is a matter of redundancy. After that, I have to do KPA on the string and the encrypted string to find the key. Which works, but I use as 15 nested for loops for brute force. Is there any other way to do this? without doing it recursively!

static String Key = null; public static void main(String[] args) { long startTime = System.nanoTime(); long startTime1 = System.currentTimeMillis(); int cntr = 0; String key = "AAAAAAAAAAADDDAM"; String plaintext = "Secretfoemotherd"; StringBuilder cipher = new StringBuilder(); StringBuilder brutus = new StringBuilder(); byte[] ciphertext = encrypt(byteT(key), byteT(plaintext)); for (int i = 0; i < ciphertext.length; i++) { cipher.append(ciphertext[i]); } while (true) { char[] nkey = new char[16]; for (int i1 = 65; i1 < 122; i1++) { nkey[0] = (char) i1; for (int i2 = 65; i2 < 122; i2++) { nkey[1] = (char) i2; for (int i3 = 65; i3 < 122; i3++) { nkey[2] = (char) i3; for (int i4 = 65; i4 < 122; i4++) { nkey[3] = (char) i4; for (int i5 = 65; i5 < 122; i5++) { nkey[4] = (char) i5; for (int i6 = 65; i6 < 122; i6++) { nkey[5] = (char) i6; for (int i7 = 65; i7 < 122; i7++) { nkey[6] = (char) i7; for (int i8 = 65; i8 < 122; i8++) { nkey[7] = (char) i8; for (int i9 = 65; i9 < 122; i9++) { nkey[8] = (char) i9; for (int i10 = 65; i10 < 122; i10++) { nkey[9] = (char) i10; for (int i11 = 65; i11 < 122; i11++) { nkey[10] = (char) i11; for (int i12 = 65; i12 < 122; i12++) { nkey[11] = (char) i12; for (int i13 = 65; i13 < 122; i13++) { nkey[12] = (char) i13; for (int i14 = 65; i14 < 122; i14++) { nkey[13] = (char) i14; for (int i15 = 65; i15 < 122; i15++) { nkey[14] = (char) i15; for (int i16 = 65; i16 < 122; i16++) { nkey[15] = (char) i16; cntr++; byte[] brutusCipher = Crack( byteC(nkey), byteT(plaintext)); for (int k = 0; k < brutusCipher.length; k++) { brutus.append(brutusCipher[k]); } if (brutus .toString() .equals(cipher .toString())) { System.out .println("found it"); System.out .println("Key: " + Key); System.out .println("Brutus: " + brutus); System.out .println("i ran: " + cntr + "times"); long endTime = System .nanoTime(); System.out .println("time:" + (endTime - startTime) + " ns"); long endTime1 = System .currentTimeMillis(); System.out .println("Took " + (endTime1 - startTime1) + " ms"); return; } brutus.setLength(0); } } } } } } } } } } } } } } } } } } public static byte[] byteT(String s) { return s.getBytes(); } public static byte[] byteC(char[] s) { StringBuilder temp = new StringBuilder(); for (int i = 0; i < s.length; i++) { temp.append(s[i]); } Key = temp.toString(); return temp.toString().getBytes(); } public static byte[] encrypt(byte[] key, byte[] plaintext) { byte[] d = new byte[key.length]; System.out.println(key.length); for (int i = 0; i < key.length; i++) { d[i] = (byte) (key[i] ^ plaintext[i]); } return d; } public static byte[] Crack(byte[] key, byte[] plaintext) { byte[] n = new byte[key.length]; for (int i = 0; i < key.length; i++) { n[i] = (byte) (key[i] ^ plaintext[i]); } return n; } } 

Answer 1

Here is my suggestion on how you can improve your code:

 char[] nkey = new char[16]; for (int i =0 ;i<16;++i) { nkey[i] = 65; } while (true) { //... do the stuff you do in the inner of the cycle int index = 15; nkey[index]++; while (index >= 0 && nkey[index] >= 122) { nkey[index] = 65; index--; if (index < 0) { break; } nkey[index]++; } } 

You can imagine what I am doing, representing what you are repeating as a number in the base 122-65 and adding it to it.

Answer 2

You can create such a class (not tested):

 class IncrementableCharArray { private final char[] array; IncrementableCharArray(int size) { array = new char[size]; Arrays.fill(array, 'A'); } boolean increment() { //here logic to increment the array int index = 0; while(index < array.length && array[index] == 'z') index++; if (index == array.length) return false; array[index]++; return true; } char[] get() { return array; } } 

Performance will not be better, but it will be a little more readable. And you can use it as follows:

 IncrementableCharArray array = new IncrementableCharArray(16); while(array.increment()) { char[] nkey = array.get(); //your test here }