In the archive there were lots of .png files, containing small QRCodes.
Each file was named with an integer number between 1-1400.
We used the qr-tools python lib to decode every QR code.
All of them were alphanumeric char, but some of them decoded to ‘+’ and 2 of them ‘=’
So we thought about base64, but this time we missed the file order.
Since the 2 ‘=’ files were respectively
189.png, the sorting wasn’t by filename.
We sorted the files for the last-modified date, the output string was ending for ‘==’ but still no flag. :(
We looked at the last-modified date for each file and some of them had the same exact epoch time, so we took those file and sort them for filename instead.
#!/usr/bin/python2 import os import glob from qrtools import QR import base64 a =  t =  for f in sorted(glob.glob("*.png"), key=os.path.getmtime): mtime = str(os.path.getmtime(f)) if mtime == '1495752115.0': a.append(int(f[:-4])) t.append(f[:-4]) a = sorted(a) for e in t: a.append(int(e)) s =  for e in a: c = QR(filename=str(e)+'.png') c.decode() print(f, c.data) s.append(c.data) print(base64.b64decode(''.join(s)))