Java tutorial
//package com.java2s; import android.util.Base64; import java.io.UnsupportedEncodingException; public class Main { public static String encryption(String pwd) throws UnsupportedEncodingException { byte[] bytes = pwd.getBytes("utf-8"); for (int i = 0; i < bytes.length; i++) { if (i % 2 == 0) { bytes[i] += 1; } else { bytes[i] -= 1; } } return Base64.encodeToString(bytes, Base64.DEFAULT); } }