it is a 64 bit elf file.
If we run it want to some input and produces Key
Open it with ghidra. at genserial function some check for if input is 0x6c61736b612121 or not to call octal function.
if convert hexs to ascii at cyberCHef, you see hidden input is laska!!. Then run with laska!!
It produce some big output different than normal ones 1639171916391539162915791569103912491069173967911091119123955915191639156967955916396391439125916296395591439609104911191169719175
octal funtion in ghidra, copy DAT_00102060 into local_218.
At the second while it print every 4. element of local_218
From the function name I gues output in octal format and also chr(octal(163)) is s and 9's are delimeter because there is no '9' in octal format.
I write basic python to convert into octals to char
arr="163917191639153916291579156910391249106917396791109111912395591519163915696795591639639143912591629639559143960910491119116
9719175"
for i in arr.split('9'):
print(chr(int(i,8)),end="")
print()
Flag : syskronCTF{7HIS-isn7-s3cUr3-c0DIN9}