Overview

A magnetic card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The data on the stripe is read by swiping against a magnetic reading head. Magnetic stripe cards are commonly used in credit cards, identity cards, and transportation tickets.

Principle

A magnetic stripe is composed of a string of magnetic domains, each oriented in a way such that opposite poles are adjacent. In the areas where two magnets with like poles are touching, there is a concentration of magnetic flux which induces a current spike as they pass a magnetic read head. Each bit of information has the same physical length on the strip. The presence or absence of an additional peak in the middle of the bit determines whether it is a one or a zero. On a magnetic stripe, a one is comprised of a single magnet that is two units long and a zero is comprised of two magnets that are each one unit long. This encoding scheme is known as F2F encoding (or Aiken BiPhase).

Data Format

Track 1 – IATA

The data standard for Track 1 was developed by the International Air Transportation Association (IATA) and contains alphanumeric information. For example, on a credit card, this track typically contains the card holder’s name as embossed on the front of the card. The specification allows up to 79 characters. Each character is 7 bits long, comprising a 6 bit character code and a parity bit.

Control Characters:
SS = Start Sentinel % FS = Field Separator ^ FC = Format Code
ES = End Sentinel ? LRC = Longitudinal Redundancy
The Track 1 data format includes the following items:
1. Approximately 62 leading clocking zeros.
2. The Start Sentinel "%" (SS).
3. Up to 76 alphanumeric characters.
4. The end sentinel "?"(ES).
5. The LRC (longitudinal redundancy check character).
6. Trailing clocking zeros (minimum of 62) to the end of the card.
Each data character is in a 7-bit (6 plus parity) alphanumeric format. The data is in the format "parity, 32, 16, 8, 4, 2, 1". Parity is odd (an odd number of "one's" in each character). The character is written "backwards" on the card starting with the least significant digit and ending with the parity bit. The card data format is "1, 2, 4, 8, 16, 32, parity".
Example: Track1Information read on a Credit card.
%B0123456789101112^ABCDEF/PQRST^01020304050607080910?8

Track 2 – ABA

The data standard for Track 2 was developed by the American Bankers Association (ABA), and contains numeric information only. On a credit card, this track typically contains the card holder's credit card number as embossed on the front of the card. The specification allows up to 40 digits. Each digit is 5 bits long, comprising a 4-bit BCD digit and a parity bit. .

The Track 2 data format include the following items:
1. Leading clocking zeros: Approximately 22.
2. The Start Sentinel ";" (SS).
3. Up to 37 hexadecimal numeric characters.
4. The end sentinel "?"(ES).
5. The LRC (longitudinal redundancy check character).
6. Trailing clocking zeros: A minimum of 22 (track 2) to the end of the card.
Each data character is in a 5-bit (4 plus parity) numeric format. The data is in the format "parity, 8, 4, 2, 1. Parity is odd (an odd number of one's in each character).
Example: Track2 Information read on a Credit card.
;0123456789101112=01020304050607080910?: