def decode_track(encoded): """Extracts raw data and verifies LRC""" if len(encoded) < 4: return None # Expected format: S data E checksum start_sentinel = encoded[0] end_sentinel = encoded[-2] checksum = encoded[-1] data_part = encoded[1:-2]
def read_track(self, track_num): if track_num == 1: return self.track1 elif track_num == 2: return self.track2 elif track_num == 3: return self.track3 else: raise ValueError("Track must be 1, 2, or 3") magcard write read utility program
For example, a USB keyboard wedge reader would just capture swiped data as if typed – no special driver needed. A writer would require sending track data in a proprietary command format over USB HID or serial. | | Sentinel & LRC | Simulates magnetic
def clear(self): self.track1 = "" self.track2 = "" self.track3 = "" def encode_track(data, start_sentinel='%', end_sentinel='?'): """Adds start/end sentinels and LRC (simple XOR checksum)""" lrc = 0 for ch in data: lrc ^= ord(ch) checksum_char = chr(lrc % 128) # simple printable approximation return f"start_sentineldataend_sentinelchecksum_char" | Extending to real hardware To use actual
python magcard_util.py --read 1 | Feature | Description | |--------|-------------| | ISO 7811 compliance | Enforces valid character sets and max lengths per track. | | Sentinel & LRC | Simulates magnetic stripe encoding with start/end sentinels and XOR checksum. | | Read/Write abstraction | Easy to replace MagCard class with real hardware driver (serial/HID). | | Error handling | Prevents invalid data from being written. | Extending to real hardware To use actual magnetic stripe readers/writers (e.g., MagTek, IDTECH, HID Omnikey), replace the MagCard class methods with device-specific commands – typically via serial or pyusb .
def is_valid_track(self, track_num, data): if track_num == 1: return all(ch in TRACK1_CHARSET for ch in data) and len(data) <= TRACK_MAX_LEN[1] elif track_num == 2: return all(ch in TRACK2_CHARSET for ch in data) and len(data) <= TRACK_MAX_LEN[2] elif track_num == 3: return all(ch in TRACK3_CHARSET for ch in data) and len(data) <= TRACK_MAX_LEN[3] return False
TRACK_MAX_LEN = 1: 79, 2: 40, 3: 107 class MagCard: def init (self): self.track1 = "" self.track2 = "" self.track3 = ""