ltrace ./keygen providing any input that is 7 characters or longer we can see that it's comparing it with laska!!

running the binary with that input returns this string: 1639171916391539162915791569103912491069173967911091119123955915191639156967955916396391439125916296395591439609104911191169719175

Then using this tool https://www.dcode.fr/code-ascii gives us the flag syskronCTF{7HIS-isn7-s3cUr3-c0DIN9}