unhec.py

#!/usr/bin/env python

from base64 import standard_b64decode
from pathlib import Path
import sys

try:
    from Crypto.Cipher import AES
    from Crypto.Util.Padding import unpad
except ImportError:
    sys.exit("Install pycryptodome: pip install pycryptodome")

if len(sys.argv) != 2:
    sys.exit("Usage: unhec.py file.hec")

path = Path(sys.argv[1])
data = path.read_bytes()

if not data.startswith(b"HSENC2"):
    sys.exit("Input does not appear to be HECed")

data = standard_b64decode(data[6:])

KEY = b"\xd7\xa6\x8d\xef\x0fJ\x12A\x94\x0fl\xb8\x01q!\xd1_\x0e&\x82\xe2X\xc9\xf7U>pn\x83I#\xb7"
IV = b"\x0ee\x19)u0X7\x08a*(#f8D"

cipher = AES.new(KEY, AES.MODE_CBC, IV)
data = unpad(cipher.decrypt(data), 16)
data = data.replace(b" ", b"\n")

out_path = path.with_suffix(".hex")
out_path.write_bytes(data)

print(f"Wrote {out_path}")