script to generate LEGO Minifigure Factory box

legobox_generator.rb

def add_zero(number)
  number.size == 1 ? "0#{number}" : number
end

def byte_check_calculator(byte_string)
  # execute a xor on the bytes of the string
  byte_string.split(" ")
    .map { |item| item.to_i(16) }
    .reduce { |acc, item| acc ^ item }.to_s(16).upcase
end

# byte 0, 3, 4 and 5 have been hidden to prevent skiddies :)

uid_byte0 = "AA"
uid_random_byte1 = add_zero(rand(0..254).to_s(16).upcase)
uid_random_byte2 = add_zero(rand(0..254).to_s(16).upcase)
uid_byte3 = "BB"
uid_byte4 = "CC"
uid_byte5 = "DD"
uid_byte6 = "9#{rand(0..1)}"

random_signature = 32.times.map { add_zero(rand(0..254).to_s(16).upcase) }.join(' ')

# CT byte is defined as 88h according to ISO/IEC 14443-3
# the byte check specs can be found here: https://www.nxp.com/docs/en/data-sheet/MF0ULX1.pdf
cascade_tag_byte = "88"
check_byte0 = add_zero(byte_check_calculator("#{cascade_tag_byte} #{uid_byte0} #{uid_random_byte1} #{uid_random_byte2}"))
check_byte1 = add_zero(byte_check_calculator("#{uid_byte3} #{uid_byte4} #{uid_byte5} #{uid_byte6}"))

# Page 3 is 8.5.4 OTP bytes set to 0 by default

output = <<~PAYLOAD
Filetype: Flipper NFC device
Version: 3
# Nfc device type can be UID, Mifare Ultralight, Mifare Classic, Bank card
Device type: Mifare Ultralight 11
# UID, ATQA and SAK are common for all formats
UID: #{uid_byte0} #{uid_random_byte1} #{uid_random_byte2} #{uid_byte3} #{uid_byte4} #{uid_byte5} #{uid_byte6}
ATQA: 00 44
SAK: 00
# Mifare Ultralight specific data
Data format version: 1
Signature: #{random_signature}
Mifare version: 00 04 03 01 01 00 0B 03
Counter 0: 0
Tearing 0: BD
Counter 1: 0
Tearing 1: BD
Counter 2: 0
Tearing 2: BD
Pages total: 20
Pages read: 20
Page 0: #{uid_byte0} #{uid_random_byte1} #{uid_random_byte2} #{check_byte0}
Page 1: #{uid_byte3} #{uid_byte4} #{uid_byte5} #{uid_byte6}
Page 2: #{check_byte1} 48 30 00
Page 3: 00 00 00 00
Page 4: 31 30 30 30
Page 5: 30 FF FF FF
Page 6: 00 00 00 00
Page 7: 00 00 00 00
Page 8: 00 00 00 00
Page 9: 00 00 00 00
Page 10: 00 00 00 00
Page 11: 00 00 00 00
Page 12: 00 00 00 00
Page 13: 00 00 00 00
Page 14: 00 00 00 00
Page 15: 00 00 00 00
Page 16: 00 00 00 FF
Page 17: 00 05 00 00
Page 18: FF FF FF FF
Page 19: 00 00 00 00
Failed authentication attempts: 0
PAYLOAD

puts output