What's With This Magnetic Stripe Stuff?
Why are we talking about magnetic
Another article on magnetic stripe
technology? Why is it that you should spend any time looking at
that? If this is your reaction to seeing an article on magnetic
stripe technology then maybe you are missing the boat. Magnetic
stripe technology has been around for a long time but many
things are changing in the technology and many of the old
reasons for not using it are no longer valid.
Where is magnetic stripe used?
Magnetic stripes are increasingly used in
many areas. Some examples of the use of the technology range
from the familiar credit and debit cards, transit tickets, and
access control cards to some applications you may not have been
aware of. Telephone debit cards have a value associated with the
card which is decremented every time the card is used. This
information is stored on the magnetic stripe and is changed with
every phone call. The new Airline Ticket Boarding Passes have a
magnetic stripe on the back. If you have a card type ticket (not
the old flimsy red tickets), you probably have a magnetic stripe
on the back. The stripe is used to hold information about you
and your flight. The latest new use for magnetic stripe is on
your drivers license. If you live in California, you already
have a magnetic stripe on your license. New York and Virginia
will soon follow. The stripe will allow error free
identification of you when it is swiped through a terminal. This
eliminates typing errors in copying from the license.
As you can see, magnetic stripe technology is all around us,
Is there something new?
you consider that magnetic stripes have been used since the
early 1960s on transit tickets and since the 1970s for bank
cards and that the same technology continues to be used on
bank cards then maybe we need something new. In fact there
have been several technology improvements over the years
that are in use in some systems today.
The two biggest changes that come to mind are security and
data permanence. Magnetic stripe has always been cited as
being insecure. Today there are technologies that can
provide many different degrees of security as discussed
The buzz word of today in magnetic stripe is high
coercivity. This is a technical term used to define how easy
(or difficult) it is to encode the magnetic stripe. A
standard bank card has a coercivity of 300 Oersteds, high
coercivity stripes range from 2700 to 4000 Oersteds.
What about security?
The major complaint about magnetic stripe technology has
always been - "but it is not secure". This is true with a
conventional magnetic stripe system. Many people have
demonstrated over the years how to counterfeit or duplicate
magnetic stripe encoding. Now there are three companies
publicizing technologies that have a solution to data security.
These are ValuGard® from Rand McNally, Watermark Magnetics® from
Thorn Secure Science International, and XSec® from XTec, Inc.
What do these technologies buy you? They each have a means
to ensure that the card or ticket being used is the original
card that had the data encoded on it. They use different means -
ValuGard uses the inherent signal amplitude properties of the
stripe, Watermark Magnetics uses a special magnetic stripe, and
XSec uses the inherent jitter properties of the stripe. What all
this means is that the actual piece of magnetic stripe can be
tied to the encoding to prevent fraud.
Loss of data
You may hear the word security used when
someone talks about high coercivity but this is confusing. It
suggests that a high coercivity stripe is harder to duplicate or
counterfeit and unfortunately this is not true. What is true is
that the stripe is less likely to be damaged by contact with a
magnet such as on a purse clasp. Some of you may remember the
big "eel skin wallet" scare of a few years ago. The story went
that eel skin wallets erased magnetic stripes on credit cards.
Obviously this was not true. Eel skin wallets are made from the
skin of the hagfish and it has no different properties than
leather or plastic. What was different about these wallets was
that they usually had a magnetic clasp. The clasp was the
culprit in destroying the encoding, but even today, many banks
will tell you that eel skin destroys magnetic encoding. With a
high coercivity stripe this would not have been a problem.
What about the other technologies? How
do they compare?
Whether magnetic stripe is used rather than
other technologies depends on the system being considered.
Obviously for a new bank card, no-one would even consider using
anything other than low coercivity magnetic stripe today. The
number of cards in use, the amount of equipment in the field and
the need to be compatible with everyone else is an over-riding
feature. But for new systems the choice is not always so clear.
The four technologies that are often
compared to magnetic stripe are: Barcode, Radio Frequency, Smart
Card, and Optical Card. Each of these are important
technologies, but there is a best technology to use in most
As a means to help identify the best
technology for any particular application, the following five
comparisons can be made: Suitability, Data Storage, Ease of Use,
Cost, and Security. An application can be rated against each of
these in turn and a table made to show the comparison.
As an example of the rating strategy, let's
take a look at one particular application, the Transit Industry,
for each of the five comparisons.
The application requires the card to
identify the type of ticket; period pass, stored ride, stored
value etc. For a simple period pass (monthly ticket) the
application only needs to check that the ticket is valid for the
current period and that it has not just been used in the
equipment (to prevent a passenger handing the ticket to another
passenger). This can all be done in a read only environment
(serial number and valid period). For the other types of
tickets, stored ride or value, the equipment will need to encode
on the ticket.
From our list of technologies, we see that
for a simple period pass, any of the five are suitable, but for
the other types of tickets barcode is not a suitable technology
as dynamic data is required and barcodes cannot be rewritten in
the field. The other four technologies all allow data to be
written and read in the field although the cost of writers for
optical technology is prohibitive and a read/write RFID tag is
not a standard "ticket" size but is a thick tag with a battery
included. Advantage: Magnetic, Smart Card.
In this application the amount of data
required is very dependent on the system requirements. At its
simplest, only the serial number and a period identifier need be
stored on the ticket. This could be only eight to ten bytes.
Conversely, the amount of data required may be quite large. If
the Transit Authority want to record the place of last use, the
issue date, original value etc. the amount of data storage
required can be several hundred bytes. Figure 1 shows a table of
the data storage available for the different technologies and as
can be seen, all have suitable amounts of data storage for the
period pass. However barcode and RFID have a problem when the
larger amounts of data are required.
The numbers shown are not absolutes but are
meant to give a guideline to available data storage. Advantage:
Magnetic, Smart Card, Optical.
* per ISO spec. - not a technology limit.
FIGURE 1: DATA STORAGE, COST, & SECURITY
FOR CARD TECHNOLOGIES
Ease of use
In the transit application, ease of use
also means speed. The last thing that the authority wants is a
line of people trying to get on a bus or go through a turnstile.
It must be possible to take the ticket, insert it in the
equipment and get it back within one to one and a half seconds.
Barcode and Radio Frequency ID have an
obvious advantage here, they are both non-contact technologies.
The ticket could be waved over a laser scanner for barcode, or
in the case of RFID it doesn't even have to be removed from the
wallet (or maybe even the pocket).
Magnetic stripe, smart card, and optical
all require contact to be made. A smart card with contacts
requires that the card be inserted in a slot and the contacts be
brought onto the ticket. The transfer of data takes place and
the card is released. The optical card has to be treated in the
same way. It is inserted in a slot and the read/write process
takes place. The card is then returned through the same slot.
The magnetic stripe card can be placed in either a swipe or
motorized reader/encoder and the ticket can be read, rewritten,
and verified in a fraction of a second. Advantage: Barcode,
This can be a big issue for an authority
that is issuing hundreds of thousands or millions of tickets a
year. Unlike hardware costs, the cost of tickets is ongoing and
must be borne as a cost of doing business. This makes the cost a
significant issue to the authority as these funds come from
operating expenses rather than a government grant. Figure 1
shows the relative costs of tickets using the various
As the table shows the only viable
solutions for this application from the cost perspective are
barcode and magnetic stripe. At a cost exceeding several dollars
per ticket for the other technologies, the cost to issue large
quantities can be prohibitive. The costs above are based on a
"credit card" sized ticket. They can vary a lot based on items
such as quantity purchased, amount of printing, base material,
etc. A barcode and a magnetic stripe can be put on paper or
plastic and the price reflects the choice of material. The other
technologies are more expensive initially and do not use the
less expensive base materials, which gives them a cost
disadvantage. Advantage: Barcode, Magnetic Stripe
Although security may not be a deciding
factor in the choice for a technology, it can be an important
issue. Security can mean many different things, but in this case
we will talk about the ability to copy or counterfeit the
ticket. This is a major concern because the ticket is the
equivalent of money. Figure 1 shows the security for the
Some caveats are necessary in the above
table. It is very easy to duplicate a simple barcode
(photocopy), but it is possible to hide the barcode behind a
panel which is transparent to infra-red but opaque to visible
light. This increases the security but the barcode can still be
copied (photographed using infra-red light and film). If the
RFID tag is a read/write tag (as may be required by the
application) the information can be easily changed unless it has
some form of permanent information in the tag.
Security on a standard magnetic stripe card
is poor but there are technologies available (such as Watermark
Magnetics, XSec, and ValuGard) which increase the security of
the magnetic stripe to near that of the Smart Card.
The Smart Card and Optical Card are both
highly secure technologies. The Smart Card uses an on-board
processor to increase the security, and the Optical Card has
such a large amount of data storage space that many types of
security can be implemented at the same time (multiple biometric
identifiers, encryption algorithms etc.). Advantage: Magnetic,
RFID, Smart Card, Optical
If we look at the five issues that have
been discussed above, we find that magnetic stripe has
advantages in all five areas. This does not mean that magnetic
stripe is the answer to all our prayers, however it does show
that with the correct specifications, magnetic stripe can be
made to meet all the requirements. Some of these category
classifications will not change from application to application
but the relative importance of each will change. For example,
cost may be the over-riding factor in choosing a technology and
you may choose a particular technology because of that even
though it does not come out best overall.
Ease of use
FIGURE 2: SUMMARY OF FEATURE ADVANTAGES
The items reviewed here may not be the only
items you will need to look at for your particular application.
These form the basis of a comparison and you can add or delete
other categories as needed.
What about Standards and Specifications?
Are they important?
The question is a far reaching one, and one
that I get asked several times a week. The answer is not as
straight forward as we would like it to be. Standards and
specifications are important, they help to ensure the quality of
a system, however they don't always have to be adhered to. What
do I mean by this? Think of your bank cards. Where would we be
if there was no global standard. At the basic level, it would
mean that your credit card may work at Macy's but not at
Gimball's. At the next level it may work in one area of the
country and not in another, or in one country and not another.
Obviously standards are a necessity in this global interchange
environment. But what if you are only making an access control
system for your building? Do you care if the cards don't work in
your neighbor's system? No. So in this case a "standard" is not
One of the most common statements, I hear
from a company looking at an ADC technology is "I can't use
magnetic stripe because I need more than 37 characters on track
2 and the manufacturers say the standard is 37 numeric
characters". The manufacturer is right in saying the standard
(there is only one recognized standard - the banking standard)
says track 2 is 37 numeric characters. But who says you have to
follow the standard. The only problem with not following the
standard (in a non-interchange environment) is that it may be
harder to get a reader or encoder capable of reading or encoding
the information you want.
Currently there is one global standard that
everyone refers to. It is ISO 7811/2 (magnetic stripe standard)
and 7811/4 and 7811/5 (track locations). The standard only deals
with low (300 Oersted) coercivity cards in the interchange
environment. These standards have recently gone through revision
and review and new versions should be published very soon. They
can be obtained from ANSI.
The ISO committee is now working on a
similar set of standards for high coercivity cards, but the
document is only in a working form at the moment and is not
likely to be released for Draft Review until next year at the
earliest. The committee still has many technical issues to
resolve. At the recent ANSI meeting, much of the time was spent
looking at the various candidates for a reference card and
trying to decide on the properties required for this card.
AIM currently publishes a document called
"AIM Guideline for Measurement of Effective Magnetic Parameters
of Magnetic Stripes on Media". This guideline presents a means
of testing a magnetic stripe on a document to determine if it
meets a set of specifications. The method uses a comparison to a
known good card as a means of defining good vs. bad and can be
used for low or high coercivity stripes. AIM is currently
working on a supplement to this to help test the immunity of the
magnetic stripe to magnetic damage.
How can I get involved? What about more
There are several ways to find out more
about standards in magnetic stripes and whether they effect you.
The first is to buy the published ANSI standards (ISO 7811/2).
This will give you a good understanding of the type of
specifications that low coercivity stripes should adhere to. A
good companion document to this is the test measurement
document, ISO/IEC 10-373, which tells how to do some of the
The next move, especially if your primary
interest is in high coercivity is to get the AIM Guideline for
Measurement of Effective Magnetic Parameters of Magnetic Stripes
on Media. This document allows you to make measurements on
magnetic stripes for yourself and determine if the stripe meets
The final move is to get involved. If you
are a manufacturer or consultant then join in and take part in
the meetings that define magnetic stripe parameters. If you are
an end user, you should consult your supplier (or consultant) to
find out the latest specifications and what part they are
playing in setting those standards.
As a summary on magnetic stripe, we have
seen that the technology offers the ability to change data in
the field, that data storage is available that will exceed most
requirements, that it is easy to use, the cost is very low, and
that full security is available if required. Magnetic stripe
technology is a proven technology that can be applied to many
different sizes and types of substrate material. This gives it a
tremendous advantage over those technologies which are more
closely bound to the substrate material.
We have taken a brief look at standards and
specifications and talked about when we need standards and when
we don't. For those of you with further questions, I invite you
to contact me and we will try to answer any questions you may