Solution by xoru:
This was a very fun challenge! I managed to write a keygen in nicely formatted C++ code for this. I hope someone finds use in this in the progress of understanding this binary. In my solution.txt file the analysis description is short, but then again there was not much to describe besides from that. A checksum algorithm with a lot of collision. I found that a string of 9 characters in the pattern [0-9a-zA-Z] yields many results. Attached is solution.txt and keygen.cpp. Compile with g++ -o keygen keygen.cpp and run ./keygen 50 to get 50 keys. I did not include the binary. Thanks for sharing!

Solution by karubabu:
thank you for the nice crackme!

Solution by jgshew:
Full pdf explanation and keygen

Solution by giganetom:
The attached python file can be called like this: ./keygen.py 50 It'll give you the 50 *unique* passwords fairly quickly. Average time on my laptop for 100K (unique) passwords is about 3 seconds, so it can generate about a 33K a second.

Solution by Frauweigel:
My python function also gives a key with the size of 9. It only searches for characters between a-z A-Z and 0-9. If it finds a ascii value that is equal to 650 it prints the key. 650 because 650 * 9 * 9 = 52650 (checksum)