simplex-decode.py

import sys, re

def main():
	filename = sys.argv[1]
	chipers_gksk = open(filename, "r").read()
	split_gksk = filename.split(".")
	the_real_flag = ""
	chiper = chipers_gksk
	while True:
		if "gksk" not in split_gksk:
			break
		chiper.replace("=== OWNED_BY_SIMPLEX ===\n", "").replace("\n=== END_OF_SIMPLEX ===\n", "")
		tmp_chiper = ""
		for c in chiper:
			s = ord(c)
			for i in range(0, 5):
				s = ( s  - 0x69) & 0xff
			tmp_chiper += chr(s)
		chiper = tmp_chiper
		split_gksk.pop()

	regx = re.search(r'GKSK{([a-zA-Z_]+)}', chiper)
	print "Flag is : ", regx.group(0)

if __name__ == '__main__':
	main()