Question

I am looking for a simple and FAST algorithm to encrypt/decrypt a string (length is about 128 bytes) with a password.

Any good algorithms?

ADDED: Custom algorithm is absolutely OK. Less memory it take – better it is (for my case). No extra classes – perfect.

Answer 1

Here is a simple encryption/decryption method. It is pretty weak, so I present it for, say education purpose:

    public static String encDec(String input, String password) {

      byte[] in = input.getBytes();
      byte[] key = password.getBytes();
      byte[] result = new byte[in.length];
      int k = 0;
      for (int i = 0; i < in.length; i++) {
         result[i] = (byte)(in[i] ^ key[k]);
         k++;
         if (k == key.length) 
           k=0;
      }

      return new String(result);
    }

It simply xors the bytes of a phrase with the bytes of a password. The same method can be used to encrypt and decrypt. Not a big challenge for a crypto analyst, by the way, but an easy start if you just need to obfuscate some data.

To make it a slightly better: don’t pass a password String but a byte array with random values. But you wanted a method with a password, that’s why I’ve implemented it that way 😉