Silly Science Electronics, Programming and Hacking About

Can you crack it? Stage 3 solution

Once getting through stage 2 you will have an EXE file. It requires windows (I ran it in a VirtualBox VM seeing as I had no idea what it would do - can't be too careful!), cygwin and the crypt library when installing cygwin.

Running the EXE you will see that you require some kind of license.txt - if you create an empty one then you get an error about it being invalid. The next stage is working out what is required to make the license.txt file valid. Being new to this realm of reverse engineering, but being comfortable with work with ASM I tried a number of tools - strace, objdump and strings. Each yielded useful bits of information - especially strings.

However the real breakthrough came when I ran the exe file through a tool called IDA Pro - the freeware version is sufficient for this exercise.

Running the binary through IDA Pro produces a very comprehensive flow of the program. If you navigate this flow you will being to see calls to printf which relate to the message we get on the screen.