## Difficulty easy - 200/500 punten (met een tool als ghidra is dit echt geen werk) ## How To Solve When you decompile the file with something like ghidra (or gdb if you are feeling naughty), you can see that the main function passes another function called *app_start* to some GTK functions. On closer inspection of this *app_start* function you can see it first checks to see if a keystore file is found and if it is it loads that file and tries to check and see if the loaded key is valid with *check_is_key_valid*. If no file was found it shows the popup via *build_license_key_popup*, in which it again uses the *check_is_key_valid* function. When looking at *check_is_key_valid* you can clearly see the format of the key has to be SHTP-AAAA-BBBB-CCCC. Where AAAA and BBBB are hex numbers that have to be larger than 256. On top of that AAAA ^ BBBB has to equal CCCC. Now you have enough information to generate your own keys. For example: "SHTP-0500-0500-0000" ## Flag IGCTF{Wh0_n33d5_RSA_wh3N_W3_h4v3_XOR}