README.md

Fore1: Hit the core

Challenge

fore1.core

Solution

Running the 'strings' command against the downloaded file gives a bunch of random-looking output, but one line in particular stands out.

$ strings fore1.core
CORE
code
./code
...
AWAVA
AUATL
[]A\A]A^A_
cvqAeqacLtqazEigwiXobxrCrtuiTzahfFreqc{bnjrKwgk83kgd43j85ePgb_e_rwqr7fvbmHjklo3tews_hmkogooyf0vbnk0ii87Drfgh_n kiwutfb0ghk9ro987k5tfb_hjiouo087ptfcv}
;*3$"
(q9e
...

Judging by the curly brackets in one of the lines, I figured the flag might be extracted from this. Upon closer inspection it becomes clear that every fifth character starting from the first A spells ALEXCTF, perhaps this correlation continues throughout? I wrote a python script to check.

#!/usr/bin/python2.7
data = "cvqAeqacLtqazEigwiXobxrCrtuiTzahfFreqc{bnjrKwgk83kgd43j85ePgb_e_rwqr7fvbmHjklo3tews_hmkogooyf0vbnk0ii87Drfgh_n kiwutfb0ghk9ro987k5tfb_hjiouo087ptfcv}"
flag = ""

for i in range(len(data)):
  if (i-3)%5 == 0:
    flag += data[i]
  else:
    continue

print flag

Sure enough the flag is returned: ALEXCTF{K33P_7H3_g00D_w0rk_up}.