marlin/buildroot/share/PlatformIO/scripts/mks_encrypt.py

import os,sys
Import("env")

from SCons.Script import DefaultEnvironment
board = DefaultEnvironment().BoardConfig()

# Encrypt ${PROGNAME}.bin and save it as build.firmware ('Robin.bin')
def encrypt(source, target, env):
  key = [0xA3, 0xBD, 0xAD, 0x0D, 0x41, 0x11, 0xBB, 0x8D, 0xDC, 0x80, 0x2D, 0xD0, 0xD2, 0xC4, 0x9B, 0x1E, 0x26, 0xEB, 0xE3, 0x33, 0x4A, 0x15, 0xE4, 0x0A, 0xB3, 0xB1, 0x3C, 0x93, 0xBB, 0xAF, 0xF7, 0x3E]

  firmware = open(target[0].path, "rb")
  robin = open(target[0].dir.path +'/'+ board.get("build.firmware"), "wb")
  length = os.path.getsize(target[0].path)
  position = 0
  try:
    while position < length:
      byte = firmware.read(1)
      if position >= 320 and position < 31040:
        byte = chr(ord(byte) ^ key[position & 31])
        if sys.version_info[0] > 2:
          byte = bytes(byte, 'latin1')
      robin.write(byte)
      position += 1
  finally:
    firmware.close()
    robin.close()

if 'firmware' in board.get("build").keys():
  env.AddPostAction("$BUILD_DIR/${PROGNAME}.bin", encrypt);
else:
  print("You need to define output file via board_build.firmware = 'filename' parameter", file=sys.stderr)
  exit(1);