Reversing challenge

Today’s post is a challenge for reverse engineering lovers.

To play, download this binary. It’s a Windows 32-bit PE executable containing a serial number validation algorithm:

Serial numbers are 16 numeric digits, taking values from 0 to 9 each. The goal of the challenge is to obtain a valid serial number without modifying the binary (i.e. to obtain second output from screenshot without manipulating the program — just by reversing the validation mechanism).

Hope you enjoy the challenge. See you!

Useful links: