Download the file and extract it.
Check the file details using the command '
file'
#file two
two: compiled Java class data, version 51.0
Executing it won't help and so we will move on to de-compile it. I used an online decompiler available in this
link
Upload the class file, decompile it and download the source, it will look like this.
import java.io.*;
public class challenge {
public challenge() { }
public static void main(string args[]) throws ioexception
{
byte abyte[] =
{ byte.valueOf((byte)106), byte.valueOf((byte)97), byte.valueOf((byte)50), byte.valueOf((byte)37), byte.valueOf((byte)36), byte.valueOf((byte)103), byte.valueOf((byte)94), byte.valueOf((byte)115), byte.valueOf((byte)94), byte.valueOf((byte)92), byte.valueOf((byte)96), byte.valueOf((byte)101), byte.valueOf((byte)94), byte.valueOf((byte)105), byte.valueOf((byte)105), byte.valueOf((byte)98), byte.valueOf((byte)107), byte.valueOf((byte)100), byte.valueOf((byte)98), byte.valueOf((byte)112), byte.valueOf((byte)92), byte.valueOf((byte)94), byte.valueOf((byte)111), byte.valueOf((byte)98), byte.valueOf((byte)92), byte.valueOf((byte)112), byte.valueOf((byte)113), byte.valueOf((byte)102), byte.valueOf((byte)105), byte.valueOf((byte)105), byte.valueOf((byte)92), byte.valueOf((byte)98), byte.valueOf((byte)94), byte.valueOf((byte)112), byte.valueOf((byte)118), byte.valueOf((byte)36), byte.valueOf((byte)38)
};
string s = "";
byte abyte1[] = abyte;
int i = abyte1.length;
for(int j = 0; j < i; j++)
{
byte byte0 = abyte1[j].byteValue(); s = (new StringBuilder()).append(s).append((char)(byte0 + 3)).toString();
}
bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(system.in));
bufferedreader.readLine();
system.exit(0);
system.out.println(s); }
}
For a quick look through in the code you can figure out that the key is stored in variable '
s' and also before the statement that print out the variable '
s'
there is an '
exit' statement '
system.exit(0)'.
So remove that line and remove the '
bufferedreader.readLine()' also.
Compile the new code and execute it.
The output will be
md5('java_challenges_are_still_easy')
Find the md5 of the text and it will be the flag.