Python script to encode / decode Gallagher card credentials

ConvertGallagherCredentials.py

import binascii
import argparse

class GallagherCredentials:
    def __init__(self, region_code, facility_code, card_number, issue_level):
        self.region_code = region_code
        self.facility_code = facility_code
        self.card_number = card_number
        self.issue_level = issue_level

def scramble(arr):
    lut = [
        0xa3, 0xb0, 0x80, 0xc6, 0xb2, 0xf4, 0x5c, 0x6c, 0x81, 0xf1, 0xbb, 0xeb, 0x55, 0x67, 0x3c, 0x05,
        0x1a, 0x0e, 0x61, 0xf6, 0x22, 0xce, 0xaa, 0x8f, 0xbd, 0x3b, 0x1f, 0x5e, 0x44, 0x04, 0x51, 0x2e,
        0x4d, 0x9a, 0x84, 0xea, 0xf8, 0x66, 0x74, 0x29, 0x7f, 0x70, 0xd8, 0x31, 0x7a, 0x6d, 0xa4, 0x00,
        0x82, 0xb9, 0x5f, 0xb4, 0x16, 0xab, 0xff, 0xc2, 0x39, 0xdc, 0x19, 0x65, 0x57, 0x7c, 0x20, 0xfa,
        0x5a, 0x49, 0x13, 0xd0, 0xfb, 0xa8, 0x91, 0x73, 0xb1, 0x33, 0x18, 0xbe, 0x21, 0x72, 0x48, 0xb6,
        0xdb, 0xa0, 0x5d, 0xcc, 0xe6, 0x17, 0x27, 0xe5, 0xd4, 0x53, 0x42, 0xf3, 0xdd, 0x7b, 0x24, 0xac,
        0x2b, 0x58, 0x1e, 0xa7, 0xe7, 0x86, 0x40, 0xd3, 0x98, 0x97, 0x71, 0xcb, 0x3a, 0x0f, 0x01, 0x9b,
        0x6e, 0x1b, 0xfc, 0x34, 0xa6, 0xda, 0x07, 0x0c, 0xae, 0x37, 0xca, 0x54, 0xfd, 0x26, 0xfe, 0x0a,
        0x45, 0xa2, 0x2a, 0xc4, 0x12, 0x0d, 0xf5, 0x4f, 0x69, 0xe0, 0x8a, 0x77, 0x60, 0x3f, 0x99, 0x95,
        0xd2, 0x38, 0x36, 0x62, 0xb7, 0x32, 0x7e, 0x79, 0xc0, 0x46, 0x93, 0x2f, 0xa5, 0xba, 0x5b, 0xaf,
        0x52, 0x1d, 0xc3, 0x75, 0xcf, 0xd6, 0x4c, 0x83, 0xe8, 0x3d, 0x30, 0x4e, 0xbc, 0x08, 0x2d, 0x09,
        0x06, 0xd9, 0x25, 0x9e, 0x89, 0xf2, 0x96, 0x88, 0xc1, 0x8c, 0x94, 0x0b, 0x28, 0xf0, 0x47, 0x63,
        0xd5, 0xb3, 0x68, 0x56, 0x9c, 0xf9, 0x6f, 0x41, 0x50, 0x85, 0x8b, 0x9d, 0x59, 0xbf, 0x9f, 0xe2,
        0x8e, 0x6a, 0x11, 0x23, 0xa1, 0xcd, 0xb5, 0x7d, 0xc7, 0xa9, 0xc8, 0xef, 0xdf, 0x02, 0xb8, 0x03,
        0x6b, 0x35, 0x3e, 0x2c, 0x76, 0xc9, 0xde, 0x1c, 0x4b, 0xd1, 0xed, 0x14, 0xc5, 0xad, 0xe9, 0x64,
        0x4a, 0xec, 0x8d, 0xf7, 0x10, 0x43, 0x78, 0x15, 0x87, 0xe4, 0xd7, 0x92, 0xe1, 0xee, 0xe3, 0x90
    ]
    return [lut[b] for b in arr]

def descramble(arr):
    lut = [
        0x2f, 0x6e, 0xdd, 0xdf, 0x1d, 0x0f, 0xb0, 0x76, 0xad, 0xaf, 0x7f, 0xbb, 0x77, 0x85, 0x11, 0x6d,
        0xf4, 0xd2, 0x84, 0x42, 0xeb, 0xf7, 0x34, 0x55, 0x4a, 0x3a, 0x10, 0x71, 0xe7, 0xa1, 0x62, 0x1a,
        0x3e, 0x4c, 0x14, 0xd3, 0x5e, 0xb2, 0x7d, 0x56, 0xbc, 0x27, 0x82, 0x60, 0xe3, 0xae, 0x1f, 0x9b,
        0xaa, 0x2b, 0x95, 0x49, 0x73, 0xe1, 0x92, 0x79, 0x91, 0x38, 0x6c, 0x19, 0x0e, 0xa9, 0xe2, 0x8d,
        0x66, 0xc7, 0x5a, 0xf5, 0x1c, 0x80, 0x99, 0xbe, 0x4e, 0x41, 0xf0, 0xe8, 0xa6, 0x20, 0xab, 0x87,
        0xc8, 0x1e, 0xa0, 0x59, 0x7b, 0x0c, 0xc3, 0x3c, 0x61, 0xcc, 0x40, 0x9e, 0x06, 0x52, 0x1b, 0x32,
        0x8c, 0x12, 0x93, 0xbf, 0xef, 0x3b, 0x25, 0x0d, 0xc2, 0x88, 0xd1, 0xe0, 0x07, 0x2d, 0x70, 0xc6,
        0x29, 0x6a, 0x4d, 0x47, 0x26, 0xa3, 0xe4, 0x8b, 0xf6, 0x97, 0x2c, 0x5d, 0x3d, 0xd7, 0x96, 0x28,
        0x02, 0x08, 0x30, 0xa7, 0x22, 0xc9, 0x65, 0xf8, 0xb7, 0xb4, 0x8a, 0xca, 0xb9, 0xf2, 0xd0, 0x17,
        0xff, 0x46, 0xfb, 0x9a, 0xba, 0x8f, 0xb6, 0x69, 0x68, 0x8e, 0x21, 0x6f, 0xc4, 0xcb, 0xb3, 0xce,
        0x51, 0xd4, 0x81, 0x00, 0x2e, 0x9c, 0x74, 0x63, 0x45, 0xd9, 0x16, 0x35, 0x5f, 0xed, 0x78, 0x9f,
        0x01, 0x48, 0x04, 0xc1, 0x33, 0xd6, 0x4f, 0x94, 0xde, 0x31, 0x9d, 0x0a, 0xac, 0x18, 0x4b, 0xcd,
        0x98, 0xb8, 0x37, 0xa2, 0x83, 0xec, 0x03, 0xd8, 0xda, 0xe5, 0x7a, 0x6b, 0x53, 0xd5, 0x15, 0xa4,
        0x43, 0xe9, 0x90, 0x67, 0x58, 0xc0, 0xa5, 0xfa, 0x2a, 0xb1, 0x75, 0x50, 0x39, 0x5c, 0xe6, 0xdc,
        0x89, 0xfc, 0xcf, 0xfe, 0xf9, 0x57, 0x54, 0x64, 0xa8, 0xee, 0x23, 0x0b, 0xf1, 0xea, 0xfd, 0xdb,
        0xbd, 0x09, 0xb5, 0x5b, 0x05, 0x86, 0x13, 0xf3, 0x24, 0xc5, 0x3f, 0x44, 0x72, 0x7c, 0x7e, 0x36
    ]
    return [lut[b] for b in arr]

def decode_creds(hex_card_number):
    eight_bytes = bytearray(binascii.unhexlify(hex_card_number))

    eight_bytes = descramble(eight_bytes)

    region_code = (eight_bytes[3] & 0x1E) >> 1
    facility_code = (eight_bytes[5] & 0x0F) << 12 | eight_bytes[1] << 4 | ((eight_bytes[7] >> 4) & 0x0F)
    card_number = eight_bytes[0] << 16 | (eight_bytes[4] & 0x1F) << 11 | eight_bytes[2] << 3 | (eight_bytes[3] & 0xE0) >> 5
    issue_level = eight_bytes[7] & 0x0F

    return GallagherCredentials(region_code, facility_code, card_number, issue_level)

def encode_creds(region_code, facility_code, card_number, issue_level):
    eight_bytes = [0] * 8

    eight_bytes[0] = (card_number & 0xffffff) >> 16
    eight_bytes[1] = (facility_code & 0xfff) >> 4
    eight_bytes[2] = (card_number & 0x7ff) >> 3
    eight_bytes[3] = (card_number & 0x7) << 5 | (region_code & 0xf) << 1
    eight_bytes[4] = (card_number & 0xffff) >> 11
    eight_bytes[5] = (facility_code & 0xffff) >> 12
    eight_bytes[6] = 0
    eight_bytes[7] = (facility_code & 0xf) << 4 | (issue_level & 0xf)

    eight_bytes = scramble(eight_bytes)

    return binascii.hexlify(bytearray(eight_bytes)).decode('utf-8')

def inverse_hex(hex_str):
    return ''.join(format(255 - int(hex_str[i:i+2], 16), '02x') for i in range(0, len(hex_str), 2))

def main():
    parser = argparse.ArgumentParser(description='Gallagher Credential Encoder/Decoder')
    parser.add_argument('-e', '--encode', action='store_true', help='Encode credential details to a hex card number')
    parser.add_argument('-d', '--decode', action='store_true', help='Decode a hex card number')

    parser.add_argument('-raw', '--hex-card-number', type=str, help='Hex card number to decode')
    parser.add_argument('-rc', '--region-code', type=int, help='Region code (0-15)')
    parser.add_argument('-fc', '--facility-code', type=int, help='Facility code (0-65535)')
    parser.add_argument('-cn', '--card-number', type=int, help='Card number (0-16777215)')
    parser.add_argument('-il', '--issue-level', type=int, help='Issue level (0-15)')

    args = parser.parse_args()

    if args.decode and args.hex_card_number:
        creds = decode_creds(args.hex_card_number)
        print(f"Region Code: {creds.region_code}")
        print(f"Facility Code: {creds.facility_code}")
        print(f"Card Number: {creds.card_number}")
        print(f"Issue Level: {creds.issue_level}")
    elif args.encode and all([args.region_code is not None, args.facility_code is not None, args.card_number is not None, args.issue_level is not None]):
        hex_card_number = encode_creds(args.region_code, args.facility_code, args.card_number, args.issue_level)
        print(f"Encoded Card Data: {hex_card_number.upper()}")
        print(f"Write to mf block on proxmark: {hex_card_number.lower()}{inverse_hex(hex_card_number).lower()}")
    else:
        parser.print_help()

if __name__ == "__main__":
    main()