Introduction to Magnetic Stripe & Other Card Technologies.
When we use the term "card technologies",
what do we mean? The easy answer is - any technology that can be
placed on a card. What is a card? Typically we think of our
credit or bank card but there are other sizes and materials used
for different applications. The card can be made of plastic
(polyester, pvc, or some other material) or paper, card, or even
some amalgamation of materials. The common point is that the
card is used to provide "access" to something and it includes
some form of ADC/ID (automatic data collection and
There are currently three main
technologies we think of when we mention card technologies.
These are magnetic stripe, smart cards, and optical cards.
Other technologies can be put on cards as well (such as bar
codes, touch memory, etc.). Often the card will have
printing on it which may involve technologies such as Dye
Diffusion Thermal Transfer (D2T2) direct to card printing.
I will cover optical cards and smart cards
briefly here and then explain further why magnetic stripe is
still a viable solution for many applications of card
memory cards use a technology similar to the one used for
music CDs or CD ROMs. A panel of the "gold colored" laser
sensitive material is laminated in the card and is used to
store the information.
The material is comprised of several layers that react when
a laser light is directed at them. The laser burns a tiny
hole (2.25 microns in diameter) in the material which can
then be sensed by a low power laser during the read cycle.
The presence or absence of the burn spot indicates a "one"
or a "zero". Because the material is actually burned during
the write cycle, the media is a write once read many (WORM)
media and the data is non volatile (not lost when power is
The optical card can currently store between 4 and 6.6 MB of
data which gives the ability to store graphical images such
as photographs, logos, fingerprints, x-rays, etc.. The data
is encoded in a linear x-y format and ISO/IEC 11693 and
11694 standards cover the details.
The biggest users of optical technology today are:
Medical/Healthcare; Prepaid Debit Cards; Cargo Manifests;
Admission Pass Season Tickets; Auto Maintenance records; and
Retail Purchase Cards.
Smart cards are credit card-sized plastic cards that contain
relatively large amounts of information in an imbedded
micro-chip. Smart cards differ from magnetic stripe cards in
two ways: the amount of information that can be stored is
much greater, and some smart cards can be reprogrammed to
add, delete or rearrange data.
There are several terms used to identify cards with
integrated circuits embedded in them. The terms "chip card,"
"integrated circuit card", and "smart card" really all refer
to the same thing.
There are two types of smart card. The first is really a
"dumb" card in that it only contains memory. These cards are
used to store information. Examples of this might include
stored value cards where the memory stores a dollar value
which the user can spend in a variety of transactions.
Examples might be pay phone, retail, or vending machines.
Another example of a "dumb" card is the memory that is
plugged into a Personal Computer (PC Card - used to be
The second type of card is a true "smart" card where a
microprocessor is embedded in the card along with memory.
Now the card actually has the ability to make decisions
about the data stored on the card. The card is not dependent
on the unit it is plugged in to to make the application
work. A smart purse or multi-use card is possible with this
Smart cards are the technology of choice when fairly large
databases must travel with an individual or an object. For
instance, a version of smart card technology is used to
record service histories for automobiles. The data travels
on a small tag on the owner’s key ring. It can be
reprogrammed, updated and accessed whenever the vehicle is
serviced with any of that company’s dealers.
As there is a microprocessor on the card, various methods
can be used to prevent access to the information on the card
to provide a secure environment. This security has been
touted as the main reason that smart cards will replace
other card technologies.
The microprocessor type smart card comes in two flavors -
the contact version and the contactless version. Both types
of card have the microprocessor embedded in the card however
the contactless version does not have the gold plated
contacts visible on the card. The contactless card uses a
technology to pass data between the card and the reader
without any physical contact being made. The advantage to
this contactless system is there are no contacts to wear
out, no chance of an electric shock coming through the
contacts and destroying the integrated circuit, and the
knowledge that the components are completely embedded in the
plastic with no external connections. The disadvantage to
this is that there are some limitations to the use of the
Smart cards are not new, the first patent was filed in
France in 1974 and the first cards were used in France in
1982. The technology was rapidly accepted in Europe because
the high cost of telecommunications made on-line
verification of transactions very expensive. The smart card
provided the mechanism to move that verification off line,
reducing the cost without sacrificing any of the security.
In the United States, telecommunication costs have always
been low compared to other countries. This meant that the
impetus to implement smart cards has taken longer to reach
the momentum needed.
The possible benefits of the acceptance of smart card
technology depend on the application in use. However, the
ability to move large amounts of data with little or no
increase in the security of the data will lead to many new
applications being created that we haven’t even begun to
There are many smart cards in use today throughout the
world. In 1993 approximately 330 million cards were produced
by the major manufacturers. Of this number only about 12%
were true "smart cards", the rest were simple memory cards.
This was projected to grow to approximately 580 million
cards in 1995 (about 10% being "smart") and 990 million in
1996 (approx. 10% "smart"). Of the cards issued in 1993
approx. 260 million were used in phone systems; 25 million
in health applications; and 23 million in banking. The rest
were used in various small projects and trials.
The smart card future is extremely bright. Many changes are
happening in the electronics world today that will increase
the capabilities of the technology. As the state of the art
in manufacturing integrated circuits improves, we get
smaller ICs which run on lower voltages, giving us less
power requirements and the ability to include more memory of
processing power. We also need to see an increase in the
speed that a card can be addressed. Currently the
initialization of a smart card can take several seconds and
even a single transaction may take longer than is tolerable
under some circumstances.
Magnetic stripe technology is everywhere.
We use cards with magnetic stripes on them everyday without even
thinking about it. The technology has been with us for many
years, but there are still many new things going on in the
The first use of magnetic stripes on cards
was in the early 1960’s. London Transit Authority installed a
magnetic stripe system in the London Underground (UK). By the
late 1960’s BART (Bay Area Rapid Transit) (USA) had installed a
paper based ticket the same size as the credit cards we use
today. This system used a stored value on the magnetic stripe
which was read and rewritten every time the card was used.
Credit cards were first issued in 1951, but
it wasn’t until the establishment of standards in 1970 that the
magnetic stripe became a factor in the use of the cards. Today
financial cards all follow the ISO standards to ensure read
reliability world wide and along with transit cards constitute
the largest users of magnetic stripe cards.
With the advent of new technologies many
people have predicted the demise of the magnetic stripe.
However, with the investment in the current infrastructure this
is not likely to be any time soon. Magnetic stripe technology
provides the ideal solution to many aspects of our life. It is
very inexpensive and readily adaptable to many functions. The
standardization of high coercivity for the financial markets has
provided the industry with a new lease on life. This coupled
with the advent of the security techniques now available means
that many applications can expect to be using magnetic stripe
technology for the next ten to twenty years.
What is a magnetic stripe?
A magnetic stripe is the black or brown
stripe that you see on your credit card, or maybe the back of
your airline ticket or transit card. The stripe is made up of
tiny magnetic particles in a resin. The particles are either
applied directly to the card or made into a stripe on a plastic
backing which is applied to the card.
The material used to make the particles
defines the Coercivity (see below) of the stripe. Standard low
coercivity stripes use iron oxide as the material to make the
particles, high coercivity stripes are made from other materials
like barium ferrite. These materials are mixed with a resin to
form a uniform slurry which is then coated onto a substrate. In
the case of a credit card or similar application the slurry is
usually coated onto a wide plastic sheet and dried. The coating
is very thin and the plastic allows the coating to be handled.
It is then sliced into stripe widths and applied to the card
during the card manufacturing process. The methods of
application include lamination (where the stripe and backing is
laminated into the card), hot-stamp (where a heated die is used
to transfer the oxide stripe from the backing onto the card
after the card is cut to size), and cold-peel (where the oxide
stripe is peeled from the backing, and then laminated into the
card). Each of the methods have their own advantages and are
largely irrelevant to the user of the card.
Another method of putting a stripe on a
card is direct coating. In this case, the oxide slurry is coated
onto the card (usually paper or card rather than plastic) during
the manufacturing process for the card. There can be some
manufacturing cost reductions by using this technique, though
there may also be some quality trade off.
Once the slurry is coated onto the
substrate (plastic backing or direct to card stock) the
particles in the slurry are aligned to give a good signal to
noise ratio. This is the equivalent of eliminating those pops
and bangs you hear on old tape recordings. The tape with the wet
slurry is passed through a magnetic field to align all the
particles. With the iron oxide particles this is relatively easy
for two reasons. The particles are low coercivity so do not need
a large magnetic field to orient them, and the particles are
acicular (needle shaped) with an aspect ratio of approximately
six to one. The acicular particles have an easy axis of
magnetization along the length of the particle which makes the
alignment an easy process. This process is not so easy with the
high coercivity materials. The particles used in most of the
high coercivity materials are not acicular, they are platelets.
These platelets have an easy axis of magnetization through the
plate, which means the alignment field has to stand the
particles on edge and they have to stay that way to get the best
performance from the stripe. Obviously the particles want to
fall over as soon as the field is removed from the stripe so
part of the skill in making a high quality stripe lies in
designing a process that can keep those particles on their side
until the slurry sets.
Unfortunately, the lack of alignment can
cause some major problems in the read and encode process of the
magnetic stripe. The waveshape of the read process can be
distorted by the lack of alignment. This distortion can cause
significant problems for some read systems.
In all of the above processes, the final
card has the familiar brown or black stripe on it. The stripe
can be encoded because the particles (like iron filings) can be
magnetized in either a north or south pole direction. By
changing the direction of the encoding along the length of the
stripe this allows information to be written on the stripe. This
information can be read back and then changed if required as
easily as the first encoding.
How does the magnetic stripe work?
The end-user defines the requirements for
the magnetic stripe including the signal amplitude expected, the
coercivity of the stripe, the encoding method and the bit
density. The card manufacturer uses the first two points to
select the type of magnetic material to use. The system designer
is concerned with all four of the parameters.
As explained above, the stripe is made from
many small particles bound together in a resin. The density of
the particles in the resin is one of the controlling factors for
the signal amplitude. The more particles there are, the higher
the signal amplitude. The density (or loading) combined with the
thickness give a method for controlling the amplitude. Signal
amplitude is important because it defines the design of the
readers for the cards. Standards exist (ISO/IEC 7811) which
define the signal amplitude for cards that are used in the
interchange environment (such as banking). By conforming to
these standards, a user ensures that the magnetic stripe can be
read in any financial terminal world wide.
The bit density of the information is
selected based on the user requirement. The ISO/IEC standards
(7811) give requirements for bit density for cards used in the
interchange environment. These standards define tracks one and
three as 210 bits per inch and track two as 75 bits per inch.
The bit density in conjunction with the data format (see below)
dictate how much data is encoded on each track.
How is information encoded on the
Each character that is encoded on the
stripe is made of a number of bits. The polarity of the magnetic
particles in the stripe are changed to define each bit. Several
schemes exist to determine whether each bit is a one or a zero,
the most commonly used schemes are F2F (or Aiken BiPhase) and
MFM (Modified Frequency Modulation).
The ISO/IEC 7811 standards specify F2F
encoding. In this encoding, each bit has the same physical
length on the stripe. The presence or absence of a polarity
change in the middle of the bit dictates whether it is a one or
a zero. The width of a single bit always remains the same but
some bits have an extra polarity change in the middle and these
are called ones.
MFM encoding is more complicated. This type
of encoding allows twice as much data to be encoded with the
same number of flux reversals (edges). For more details on MFM
the reader is referred to the AIM Inc. publication "Modified
Frequency Modulation (MFM) for Magnetic Stripes" available on
the AIM Inc. World Wide Web site.
The choice of encoding scheme is determined
by the application and the user. If the application is one where
conformance with ISO/IEC 7811 is necessary then F2F encoding is
the choice. For applications where large amounts of data must be
encoded, MFM may be a more suitable choice.
Once the encodation scheme is chosen, the
format of the data must be selected. ISO/IEC 7811 specifies two
different schemes for use on interchange cards. These are four
bits plus parity and six bits plus parity. The four bits allow
only the encoding of numbers plus some control characters, the
use of six bits allows the full alpha numeric set to be encoded.
The parity bit is used to help determine if an error occurred in
the reading of the data. The total number of "one" bits in a
character is added up, in odd parity this must equal an odd
number. If the total is odd, the parity bit is set to a zero, if
the total is even the parity bit is set to a one.
Although the encodation schemes are defined
in ISO/IEC 7811, it is only necessary to follow them if the
application requires conformance with 7811. Some applications
depart from this scheme by allowing different bit
density/encoding scheme combinations, others depart
significantly by using "proprietary" schemes down to the bit
level. As an example, an identification card may use two bits to
determine eye color (00 = blue, 01 = brown, 10 = green, 11 =
other). This is much more efficient in encoding space, but means
the data cannot be read in a standard interchange terminal. For
some applications this is not important and the extra space
available is very important.
What is coercivity?
Measured in Oersteds, coercivity is the
measure of how difficult it is to encode information on the
magnetic stripe. A standard bank card has a coercivity of
approximately 300 Oe (Oersteds) and is considered to be low
coercivity. In Japan there is a second stripe on the credit
cards with a coercivity of 600 Oe. The trend is to move towards
higher coercivity with values of 2100, 2750, 3600 and 4000
Oersteds being common. High coercivity magnetic stripes bring a
new collection of parameters to the magnetic stripe world and
higher is not always better.
Initial coercivity is defined by the type
of particles used to manufacture the stripe. Gamma Ferric Oxide
will give you a low coercivity stripe, Barium Ferrite will give
you a high coercivity stripe. The material alone does not define
the final coercivity of the stripe as the manufacturing process
will change the value usually in the downwards direction. It is
possible to raise the coercivity of particles by including other
agents in the slurry.
Coercivity is NOT a measure of signal
amplitude. Early versions of high coercivity stripes often had
high signal output. This is not a requirement of high coercivity
and is not usually a good thing. Most readers available today
are setup to read signal levels similar to those defined in the
ISO/IEC 7811 standard. Keeping the signal output in this range
makes the range of available readers much greater.
Early versions of the high coercivity
magnetic stripe were marketed with the name High Energy. This
name suggests high output levels and often causes confusion
amongst users of the technology.
Why would I use high coercivity?
The advantage of high coercivity is that it
is harder to encode the information on the stripe. This also
means that the it is more difficult to erase the information and
so problems of accidental erasure are diminished. It is still
possible to erase the information, but common household magnets
are not usually powerful enough. This means the person who puts
the transit card on the refrigerator will not usually damage the
encoding on the stripe.
The disadvantage is that although the
encoding can be read in a standard low coercivity reader the
encoder must be designed to encode high coercivity stripes.
Is higher coercivity better?
Although the coercivity is a factor in
erasing a stripe, it is by no-means the only factor. When a
stripe is declared to be a 4000 Oersted (Oe) stripe, it really
means that the nominal value is 4000 Oe. There are also lots of
particles in that stripe with coercivities of other values. The
distribution of the coercivities will typically follow a bell
shape curve. The steepness of the bell shape defines the
percentage of particles at the stated value, a sharp (steep)
curve shows that are a large percentage are the nominal value. A
flat curve shows that there are many other coercivities present
in the stripe. This is important because it is used to define
something called "squareness" of the stripe.
Squareness is a parameter that can be used
to help define the susceptibility of a stripe to erasure. A 2700
Oe magnetic stripe with high squareness (sharp curve) has a
large number of particles at the nominal coercivity. To erase
that stripe, a magnetic force greater than the coercive value
will have to be applied to the stripe. Another stripe with low
squareness may have a higher nominal coercivity but because
there may be a large proportion of low coercivity particles it
may be very easy to erase the stripe.
Who uses magnetic stripe cards?
Everyone uses magnetic stripes. The most
visible use is your bank (credit, debit, and ATM) cards, but
these are not the only places. Take a look at your Airline
Ticket and Boarding pass (ATB) the next time you travel. Many of
these are now including magnetic stripes on the cards. Other
places include your phone card, your transit (bus or train)
ticket, and even your parking lot ticket.
Are all magnetic stripes the same?
Magnetic stripes are not all the same. On
the outside they are all made of a magnetic material coated in
some way on the document. However, as explained above, there are
different ways to coat the material on the document and
different ways to make the magnetic material. These all affect
the performance of the material in some way.
The properties of the magnetic stripe are
all defined during the manufacturing process. These properties
define the signal strength of the encoding, the coercivity of
the stripe, the ability to resist erasure, even the waveshape of
the recording. These parameters are not controlled by the user
but they can have a tremendous effect on the performance of the
system and should be defined by the user.
Even the method of coating the magnetic
material on the document can influence the performance of the
stripe. A direct coating on a paper ticket may produce a stripe
that is much more abrasive than the stripe on a laminated
plastic card. This abrasiveness will affect the life of the
magnetic heads being used.
Some magnetic stripes have coatings over
the stripe to protect the stripe from abrasion thus prolonging
the life of the stripe on the card or ticket. This coating may
affect the performance of the stripe in other ways.
Are there standards for magnetic stripe
Yes there are. The most commonly quoted
standards are the ISO/IEC 7810, 11, 12 and 13 series of
standards. These standards are written for the credit and debit
card market and so include information on the embossed
characters on the cards as well as the track locations and
information on the magnetic stripe. ISO/IEC 7811 has six parts
with parts two and six specifically about low and high
coercivity magnetic stripes. These standards include information
on the magnetic properties that guarantee that the stripe can be
read in a magnetic stripe reader in the U.S.A. as well as in
Japan. The companion to the ISO/IEC 7811 series of standard is
ISO/IEC 10 373. This document details the test methods for the
ISO/IEC 7811 series of standards.
Work is just about to start on three new
American National Standards (ANSI) standards that relate to
magnetic stripe performance. These are:
Magnetic Parameters of Magnetic Stripes
Magnetic Parameter Values for Applications
Readers and Encoders - Equipment Specifications
The first two of these new standards are
related to the AIM Inc. published document listed above, turning
it into an ANSI standard. The third item is work that is new in
the magnetic stripe world in that the goal is to create the
first standards that are relevant to the equipment
manufacturers. Details are available from the AIM Inc. office.
What if I want to do something
If you are not intending to use your cards
in the banking system then you can do anything you want. The
ISO/IEC 7811 series of standards define track one as a read only
track with 210 bits per inch and 6 bits plus a parity bit per
character. This allows for a full alpha-numeric encoding. Track
two and three both use four bits plus a parity bit (number
characters plus A to F) only, with track two at 75 bits per inch
and track three at 210 bits per inch. If you don’t have cards
that have to be read in the banking system then you can use any
encoding scheme and bit density on any track you wish. In fact
this gives you some added security, as it makes it more
difficult for someone to copy your cards.
I have heard that magnetic stripe it is
not secure - it is this true?
Magnetic stripes are not inherently secure.
The problem with being easy to manufacture and encode is that it
also makes it easy for the crooks to do the same. Several
schemes are available for creating a secure encoding on a
magnetic stripe, Watermark Magnetics, XSec, Holomagnetics,
XiShield, Jitter Enhancement, ValuGard, and MagnePrint are a
few. The contacts for some of these technologies are listed
below. Each of these technologies exploits some aspect of the
magnetic stripe, the card, and the data on the stripe to tie
everything together to make counterfeiting the card in some
fashion very difficult.
How do these Security Methods Work?
The security schemes all work in basically
the same way. They focus on some part of the card/magnetic
stripe/encoding and record the information that makes it
different from any other card. This could be the noise in the
magnetic stripe, an intentional permanent signature in or on the
stripe, or some external feature on the card that is permanent.
The advantage to using one of these
techniques is that the card and data become tied together making
the duplication of the data very difficult. The disadvantage to
these techniques is that they cost money and are for the most
part, proprietary. Several of the techniques have been used in
large applications where the system demanded some form of extra
Why do "Eel Skin Wallets" cause problems
for magnetic stripes?
This is a rumor that started during the mid
1980's at a time when eel skin wallets had become very
fashionable. The most common way of providing a clasp on these
wallets was to use a magnet. This magnet was usually powerful
enough to erase a magnetic stripe if the two came into contact.
The popular press picked up the problem and very quickly the
rumor that the eel skin was capable of damaging the magnetic
information was spread. In fact the eel skin is no different
from any other kind of leather and was not the problem, the
magnet was the sole cause of the problems.
My card does not work in my ATM. What
did I do to it?
This is a complicated question to answer
that can only be properly answered after the card has been
analyzed by some test equipment. The likely problems are dirty
or scratched stripe, or erased stripe. The stripe on a card is
not delicate but a few simple measures will increase the life of
the stripe. Try to keep the card in a clean place when you are
not using it. A gritty wallet, kept in the back pocket of a pair
of pants, will probably end up scratching the stripe (and
probably warping the card). A scratched or dirty card will
eventually not work.
Keep the card away from magnets. The two
most likely examples of magnets we see are the refrigerator
magnet and the Electronic Article Surveillance (EAS) Tag
demagnetizer in a store (this is the box that some stores have
on the check out counter that they pass a book or clothes over
so that you do not set the alarms off when you leave the store).
Stephen G. Halliday
The above paper was originally presented at,
SCAN-TECH ASIA 97, Singapore, April 24, 1997