I was thinking of a way to hide complex algorithms in source code and it turns out that Java Compiler can compile source code with unicode code character encoding. So for instance a typical HelloWorld class like this
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
Can be written as
\u0070\u0075\u0062\u006C\u0069\u0063\u0020\u0063\u006C\u0061\u0073\u0073\u0020\u0048\u0065\u006C\u006C\u006F\u0057\u006F\u0072\u006C\u0064\u0020\u007B\u0009\u0070\u0075\u0062\u006C\u0069\u0063\u0020\u0073\u0074\u0061\u0074\u0069\u0063\u0020\u0076\u006F\u0069\u0064\u0020\u006D\u0061\u0069\u006E\u0028\u0053\u0074\u0072\u0069\u006E\u0067\u005B\u005D\u0020\u0061\u0072\u0067\u0073\u0029\u0020\u007B\u0009\u0009\u0053\u0079\u0073\u0074\u0065\u006D\u002E\u006F\u0075\u0074\u002E\u0070\u0072\u0069\u006E\u0074\u006C\u006E\u0028\u0022\u0048\u0065\u006C\u006C\u006F\u002C\u0020\u0057\u006F\u0072\u006C\u0064\u0021\u0022\u0029\u003B\u0009\u007D\u007D
And it would compile just fine using javac and will run and print Hello, World!. I wrote a small application which converts any java source file to Unicode encoding so that you can hide your source within your computer from people who have access.
import java.io.*;
/*
* @author Shazin Sadakath
*/
public class JavaUnicodeEncoding {
public static void main(String[] args) throws Exception {
BufferedReader br = null;
BufferedWriter bw = null;
try {
br = new BufferedReader(new FileReader(args[0]));
bw = new BufferedWriter(new FileWriter(args[1]));
String line = null;
while((line = br.readLine()) != null) {
for(char c:line.toCharArray()) {
bw.write(String.format("\\u%04X",(int) c));
}
bw.flush();
}
} catch(ArrayIndexOutOfBoundsException e) {
usage();
} catch(Exception e) {
System.err.println(e.getMessage());
} finally {
if(br != null) {
br.close();
}
if(bw != null) {
bw.close();
}
}
}
private static void usage() {
System.out.println("java JavaUnicodeEncoding <input class filename /> <output class filename/>");
}
}
public class HelloWorld {
public static void main(String[] args) {
\u0053\u0079\u0073\u0074\u0065\u006D\u002E\u006F\u0075\u0074\u002E\u0070\u0072\u0069\u006E\u0074\u006C\u006E\u0028\u0022\u0048\u0065\u006C\u006C\u006F\u002C\u0020\u0057\u006F\u0072\u006C\u0064\u0021\u0022\u0029\u003B
}
}
Hi,
ReplyDeleteWhen decompile dex to jar original source code will visible.
You can not hide source code byr this method!