Solution for a DEFCON 26 Biohacking Village CTF challenge

bacnetlightingxfil.py

#!/usr/local/bin/python3

import binascii
import pyshark

set_brightness_cap = pyshark.FileCapture('bacnetlightingxfil.pcap',
    display_filter='bacnet && (bacapp.confirmed_service == 15) && (bacapp.type == 0)'
)

vals = [ int(packet.bacapp.present_value_real) for packet in set_brightness_cap ]

print("\t".join(map(str, vals)))

encoded_bits = [ 1 if x>95 else 0 for x in vals ]

n = int('0b%s' % "".join(map(str, encoded_bits)), 2)

res = binascii.unhexlify('%x' % n)

print(res)