magstripe-rs

A robust Rust library and CLI tool for decoding magnetic stripe card data from raw binary streams. Supports multiple track formats and encoding schemes commonly found in magnetic stripe cards.

Features

• Multiple Track Format Support

  • Track 1 (IATA format, 7-bit alphanumeric)
  • Track 2 (ABA format, 5-bit numeric)
  • Track 3 (THRIFT format, 5-bit numeric)

• Encoding Variants

  • Standard and inverted bit patterns
  • LSB-first and MSB-first bit ordering
  • Configurable parity (odd/even)
  • Raw mode for non-standard cards

• Robust Decoding

  • Automatic format detection
  • Start/end sentinel detection
  • Parity checking
  • LRC (Longitudinal Redundancy Check) validation

• Flexible Input

  • Decode from raw byte arrays
  • Support for partial/damaged data
  • Configurable bit stream lengths

Installation

Add to your Cargo.toml:

[dependencies]
magstripe-rs = "0.1.0"

Library Usage

Basic Decoding

use magstripe_rs::{BitStream, Decoder, Format};

// Raw magnetic stripe data
let data = vec![255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192];
let bit_count = 130;

// Create a bit stream
let stream = BitStream::new(&data, bit_count).unwrap();

// Set up decoder with desired formats
let formats = vec![
    Format::Track2,
    Format::Track2Inverted,
];
let decoder = Decoder::new(&formats);

// Decode the data
match decoder.decode(stream) {
    Ok(output) => {
        println!("Format: {:?}", output.format);
        println!("Data: {}", output.data);
    }
    Err(e) => {
        eprintln!("Decode error: {:?}", e);
    }
}

Custom Format Specification

use magstripe_rs::{Format, FormatSpec, ParityType, Decoder, BitStream};

let custom = FormatSpec {
    bits_per_char: 5,
    start_sentinel: Some(0b11010),
    end_sentinel: Some(0b11111),
    lsb_first: true,
    parity: ParityType::Odd,
    inverted: false,
};

let decoder = Decoder::new(&[Format::Custom(custom)]);

CLI Usage

Basic Usage

# Decode with automatic format detection
magstripe-decode "[255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192]" -b 130

# Verbose output with tracing
magstripe-decode "[255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192]" -b 130 -v

# Try specific formats
magstripe-decode "[255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192]" -b 130 -f Track2Inverted

Command Line Options

• -b, --bits <count>: Number of bits to process from the input
• -f, --format <format>: Specific format to try (default: tries all)
• -v, --verbose: Enable verbose output with tracing

Available Formats

• Track1: Standard Track 1 (7-bit IATA)
• Track1Inverted: Track 1 with inverted bits
• Track2: Standard Track 2 (5-bit ABA)
• Track2Inverted: Track 2 with inverted bits
• Track2MSB: Track 2 with MSB-first bit order
• Track2LSB: Track 2 with LSB-first bit order
• Track2Raw: Track 2 without sentinel checking
• Track2SwappedParity: Track 2 with swapped parity bits
• Track2EvenParity: Track 2 with even parity
• Track3: Standard Track 3 format

Track Format Details

Track 1 (IATA)

• 210 bits per inch (bpi)
• 7-bit character encoding (6 data + 1 parity)
• Alphanumeric character set
• Start sentinel: % (0x05)
• End sentinel: ? (0x1F)
• Format: %[data]?[LRC]

Track 2 (ABA)

• 75 bpi
• 5-bit character encoding (4 data + 1 parity)
• Numeric only (0-9, special chars)
• Start sentinel: ; (0x0B)
• End sentinel: ? (0x0F)
• Format: ;[account]=[expiry][discretionary]?[LRC]

Track 3 (THRIFT)

• 210 bpi
• 5-bit character encoding (4 data + 1 parity)
• Numeric character set
• Similar format to Track 2

Character Encoding

Track 2 Character Map (5-bit)

Character	Binary (LSB)	Hex	Decimal
0	00001	0x01	1
1	10000	0x10	16
2	01000	0x08	8
3	11001	0x19	25
4	00100	0x04	4
5	10101	0x15	21
6	01101	0x0D	13
7	11100	0x1C	28
8	00010	0x02	2
9	10011	0x13	19
;	11010	0x1A	26
=	10110	0x16	22
?	11111	0x1F	31

Error Handling

The decoder provides detailed error information:

pub enum DecoderError {
    InvalidBitStream,
    BitstreamTooShort { bit_count: usize, minimum_required: usize },
    NoStartSentinel,
    NoEndSentinel,
    ParityError { position: usize },
    LrcCheckFailed,
    NoFormatsProvided,
    NoValidFormat { attempted: usize },
    InvalidCharacterValue { value: u8, position: usize },
}

Testing

The library includes comprehensive tests for various card formats:

# Run all tests
cargo test

# Run with verbose output
RUST_LOG=trace cargo test

# Run specific test
cargo test test_track2_inverted_decode

Examples

Decoding a Real Card

use magstripe_rs::{BitStream, Decoder, Format};

// Example: Card that reads as inverted Track 2
let data = vec![255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192];
let stream = BitStream::new(&data, 130).unwrap();

let decoder = Decoder::new(&[Format::Track2Inverted]);
let output = decoder.decode(stream).unwrap();

assert_eq!(output.data, "0004048712");

Handling Unknown Formats

use magstripe_rs::{BitStream, Decoder, Format, DecoderError};

# let data = vec![255, 255, 255, 151, 222, 246, 253, 190, 141, 247, 7, 127, 255, 255, 255, 255, 192];
# let stream = BitStream::new(&data, 130).unwrap();
// Try all common formats
let formats = vec![
    Format::Track1,
    Format::Track1Inverted,
    Format::Track2,
    Format::Track2Inverted,
    Format::Track2MSB,
    Format::Track3,
];

let decoder = Decoder::new(&formats);
match decoder.decode(stream) {
    Ok(output) => println!("Success with format: {:?}", output.format),
    Err(DecoderError::NoValidFormat { attempted }) => {
        println!("Tried {} formats, none worked", attempted);
    }
    Err(e) => println!("Other error: {:?}", e),
}

Contributing

Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.

License

This project is licensed under the Mozilla Public License Version 2.0 - see the LICENSE file for details.

Safety

This library is designed for educational and legitimate testing purposes only. Always ensure you have proper authorization before reading or decoding magnetic stripe cards.

Acknowledgments

• Based on ISO/IEC 7811 standards for magnetic stripe cards
• Inspired by various open-source magnetic stripe decoding projects