PLASTIC CARD ENCODING PRACTICES AND STANDARDS
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By Hasan Ali
For P/HUN Issue #3
GENERAL PHYSICAL CHARACTERISTICS
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If you take any plastic card (MasterCard, VISA, AMEX, ATM cards, etc.) and
turn it over you will find a thin black strip of magnetic material. This
strip has the ability to hold multiple "tracks" or bands of encoded data.
There are 3 valid tracks. Track 1 is the track nearest to the top of the
card, and it is followed by Tracks 2 and 3. The original specifications
allowed for Tracks 1 and 2 only, and they are both read-only. The
additional Track 3 furnishes an ability to read OR write.
TRACK 1
The International Airlines Transport Association originated the development
of Track 1 as the official track airline use and, in fact, it defined the
data and encoding formats for the ANSI standard. This track was originally
designed to allow the use of customer-operated ticket dispensing machines
to cut down the traffic at airport ticket counters.
Now, many other parties make use of Track 1 because it is the only encoded
track that permits encoding of the card holder's name. With this alphanumeric
capacity, the card holder's name can be printed on an EFT terminal receipt
rather cheaply, otherwise the name would have to be sent the computer, which
would be more costly and would take more time.
There are 26 formats for Track 1, and they are designated by codes from "A" to
"Z". Format "B" is shown below.
Field Name Length(chars)
Start sentinel 1
Format code = "B" 1 (alpha only)
Primary account number Up to 19
Separator (SEP) 1
Country code 3
Name 2 to 26
Surname
Surname SEP = "/"
First name or initial
Space (when required)
Middle name or initial
Period (when followed by title)
Title (when used)
SEP 1
Expiration date or SEP 4 or 1
Discretionary data balance up to maximum
track length
End sentinel 1
Longitudinal Redundancy Check (LRC) 1
MAXIMUM TRACK LENGTH 79
Format code "A" is reserved for proprietary use by the card issuer. Format
codes "C" through "M" are reserved by ANSI for use in other data formats of
Track 1. Format codes "N" through "Z" are available for use by individual
card issuers.
TRACK 2
The American Bankers Association led to the development of Track 2 on behalf
of two credit card companies (Interbank and VISA) and their members. The
intent was to have a standardized plastic card which could be used at point-
of-sale (POS) terminals to obtain authorization for credit card transactions.
Today, in the financial industry, Track 2 is the most widely used encoding
method for plastic cards. It has a strong following because most EFT
terminals are connected directly to a computer that accesses the cardholder's
data files. Also, it is the preferred choice of the ABA and is the only track
recognized and supported by MasterCard and VISA.
The format of Track 2 is shown below.
Field Name Length (chars)
Start sentinel 1
Primary account number up to 19
SEP 1
Country code 3
Expiration date or SEP 4 or 1
Discretionary data balance up to maximum
track length
End sentinel 1
LRC 1
MAXIMUM TRACK LENGTH 40
Although Track 2 is widely accepted, there is a serious potential concern
about it because of its limited encoding capacity - only 40 characters. The
argument supporting the current capacity stresses that all the necessary
information to authorize a transaction is at the data center thereby
eliminating the need to encode extraneous data. On the other hand, those
suggesting that the capacity be increased feel that greater capacity would
allow certain transactions to be approved directly at the terminal, or,
at least, minimize data sent between terminal and computer for each
transaction. Those who hold this view are using Tracks 1 and 3.
TRACK 3
Track 3 was developed for use in off-line EFT terminals but was designed
to be compatible with other plastic card standards. Thus, Track 3 is
compatible with the ANSI standard for embossing plastic cards and the ANSI
standard for physical characteristics of magnetic stripes. More recently,
financial institutions have started to use it in on-line systems because
of its greater data storage capacity.
The format of Track 3 follows.
Field Name Usage Status Length (chars)
Start sentinel M S 1
Format Code M S 2
Primary account number (PAN) M S 19
SEP M S 1
Country code or SEP M S 3 or 1
Currency M S 3
Currency exponent M S 1
Amount authorized per M S 4
cycle period
Amount remaining this cycle M D 4
Cycle begin M D 4
Cycle length M S 2
Retry count M D 1
PIN control parameters or SEP M S 6 or 1
Interchange control M S 1
Type of account and M S 2
service restriction (PAN)
Type of account and M S 2
service restriction (SAN-1)
Type of account and M S 2
service restriction (SAN-2)
Expiration date or SEP M S 4 or 1
Card sequence number M S 1
Card security number or SEP M S 9 or 1
First subsidiary account O S variable
number (SAN-1)
SEP M S 1
Second subsidiary account O S variable
number (SAN-2)
SEP M S 1
Relay marker M S 1
Crypto check digits or SEP M D 6 or 1
Discretionary data O D variable
End sentinel M S 1
LRC M D 1
MAXIMUM TRACK LENGTH 107
"M" - Mandatory field "O" - Optional field
"D" - Dynamic field - may be modified by appropriate interchange partners
"S" - Static field - may only be modified by card issuer
For further information on these topics, find these ANSI publications
at your local good technical library:
ANSI X4.13-1979
ANSI X4.16-1973
ANSI X4.16-(Draft October 1980)
ANSI X9.1-1980
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