I'm a little concerned about this question, which involves analysing a Linux application that people can download from mediafire.com. In case it disappears, the essential parts are reproduced below:
Here's what we have: a decryption program which takes a string as an argument, but when we run it we just get junk back; some encrypted text, and; a weird image file of a calendar. A bizarre combination, take a look and see if you can figure it out.
here's the encrypted string: NXIS24CuEq@uEq@uEq@u
The files :-
My problem with this puzzle is that mediafire.com is currently classed as Partially dangerous by Google. It really isn't the sort of place you want to be downloading software from.
There are a lot of other sites that run CTF-style hacking contests (e.g., backdoor.sdslabs.co), but I'm sure none of them would ever ask people to install unknown software from domains that are beyond their control.
I suggest that questions inviting people to install and/or analyse software should be ruled off-topic for safety reasons.