Based on https://github.com/megabug/gallagher-research

gallagher.py

import binascii

sbox = [
    [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],
]


def flatten_sbox():
    output = {}
    for i in range(16):
        for j in range(16):
            k = i * 16 + j
            output[k] = sbox[i][j]
            key = binascii.hexlify((k).to_bytes(1, byteorder="big"))
            value = binascii.hexlify(sbox[i][j].to_bytes(1, byteorder="big"))

    return output


def load_card_from_txt(filename) -> bytes:
    """convert hex to binary object"""
    with open(filename, "r") as f:
        data = f.read().strip().replace(" ", "")

    return binascii.unhexlify(data)


def sbox_lookup(data: bytes, sbox_inv: dict) -> bytes:
    """lookup each byte in the sbox"""
    output = []
    for byte in data:
        output.append(sbox_inv[byte])

    return bytes(output)


def main():
    sbox_flat = flatten_sbox()
    sbox_inv = {v: k for k, v in sbox_flat.items()}

    card_data = load_card_from_txt("example_dump.txt")
    card_data_proc = sbox_lookup(card_data, sbox_inv)
    print(card_data_proc)
    print((card_data_proc[3] >> 1) and 0x0f)
    print(card_data_proc[7] >> 4)


if __name__ == "__main__":
    main()