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Plastic Money

You will sometimes hear someone say, in a loose conceptual sense, that credit
cards have money in them. Of course we know that that isn’t the case; our
modern plastic card payment network relies on online transactions where the
balance tracking and authorization decisions happen within a financial
institution that actually has the money (whether it’s your money or credit).
There is an alternate approach though, one which has historically been
associated with terms like “epurse” in the technology industry: what if the
balance tracking and authorization decisions were actually made inside of the
card?

Ten years ago this proposal might have seemed more absurd in the United States
(amusing since, of course, the technology to facilitate this is much older).
Payments in the US were made using magnetic cards with two tracks totally
hundreds of bits. Debit cards could contain a challenge value used to verify
the PIN, but even then the decision of whether or not to accept a PIN offline
was made entirely by the payment terminal. Fraud related to these cards became
a problem quickly enough that offline processing of card transactions (for
example by the use of a “kerchunker” impression machine) became very rare, and
all transactions were conducted online. Even then cards were vulnerable to
duplication and this was a fairly common form of fraud.

Europeans, though, had been using smart card technology dating back to as early
as the ’80s in France. These cards had an onboard microcontroller that could
make decisions and even run applications. Inside of the card there is
nonvolatile storage that can retain a cryptographic key, allowing the card to
participate in a cryptographic challenge-response process that made duplication
very difficult. Even better, PIN verification was performed inside the card,
meaning that even a malicious terminal could not accept an invalid PIN during
an offline transaction.

And today, that’s the most widespread application of smart card technology:
cryptographic challenge-response authentication. The technique is ubiquitous
both in payment systems and in access control and ID verification, spanning a
wide gamut of capabilities from DESfire keycards to the United States
Government’s behemoth of an identity credential standard, PIV.

It’s sort of interesting that these less ambitious applications of smart cards
are about as far as they’ve gotten in the United States. Their capabilities
are much greater than modern applications suggest. Smart cards were, from the
very beginning, conceived as much more powerful multi-application devices
that were capable of enough internal accounting logic to implement true
stored value cards, or SVCs. Cards which “contained” money in a balance that
could be debited and credited fully offline, just by a terminal communicating
with the card.

First, bit of history of the smart card. One of the reasons that smart cards
have made relatively little inroads in the US is their European origin. Nearly
all of the development of smart card technology happens in European companies
companies like Gemplus (Netherlands) and Axalto (France), today merged into
Gemalto, part of French defense conglomerate Thales. Not to be understated
either is the German company Giesecke+Devriant. Many early developments
happened within the French Bull group as well, which through merger into
Honeywell continues to make related products. Identity technology vendor
Morpho, later Safran Morphotrust, today Idemia, forms the backbone of the TSA
and Border Patrol’s ubiquitous travel surveillance from their headquarters in
the suburbs of Paris. They are further accused of providing identification
technology to Chinese government agencies for purposes of oppression. Identity
is a sticky business.

These companies have a long-running relationship with secure identity. G+D has
long been a major international center of expertise in currency manufacturing
and security, and the US Federal Reserve System for example relies on G+D
equipment to detect counterfeits. Gemalto became one of the primary vendors in
secure digital identity technology, and Thales carries this on today, providing
major components of the US federal government’s USAccess/HSPD-12 scheme.

It all began with payphones. Well, that’s not true, there were plenty of
developments in smart card technology before they were applied to payphones,
but payphones introduced the technology to the French masses in 1986. France
also pioneered chip-based online transactions, with a nationwide ATM network
based on smart cards in 1988 and ubiquitous issuance of a precursor to EMV in
1993. We have to be careful to differentiate online and offline systems,
though. One of the confusing issues around SVCs is their functional similarity
to online transaction cards using an integrated chip for authentication
purposes. To understand more clearly, let’s take a closer look at one of the
most common SVC applications in the US: the laundry card.

Laundromats are conceptually simple; each machine needs a coin acceptor (often
limited to quarters only) and a coin vault. In practice, it’s a little more
complex. Most customers don’t walk in with enough quarters any more, so the
laundromat has to provide a change machine. Change machines, being stocked with
hundreds of dollars in coins and bills, are an attractive target for theft.
Besides, they aren’t that reliable. Emptying the coin vaults on each machine
daily is a time sink for staff, especially when the risk of theft requires
multiple staff members as a precaution. Wouldn’t it be easier if laundromat
payments were electronic?

Today there are a number of ways to achieve that end, most of them worse than
the old system of rolls of quarters, involving some combination of QR codes,
smartphones, Bluetooth, and “The Cloud.” These approaches were a nonstarter in
the ’00s, though. Wireless networking was in its infancy, the cost of putting
network connectivity in every machine was very high. A solution was needed that
allowed the billing devices in machines to be offline, operating totally
independently. Any case of offline payment terminals calls for SVCs.

So in many laundromats even today, there is a device on the wall somewhere
called a value transfer machine, or VTM. Actually the term VTM is a trademark
of one of the major vendors of these systems, ESD, but it’s such a good generic
term that I will disregard their claim and use it across vendors. At the VTM,
a customer either inserts their smartcard or presses a button indicating that
they want to purchase one. The VTM accepts a payment by either cash or payment
card, and then “transfers” that “value” to the inserted smart card—or a new
one dispensed from an internal stack. Pricing details vary, but smart cards
aren’t as cheap as anyone would like and so it’s common to charge a few dollars
for a new card. Customers are encouraged to keep their card for the long term.

What happens internally? A very simple implementation suffices to explain the
concept. On the smart card, there is a value in nonvolatile memory that
represents the amount of money on the card. When you add money, the VTM
increments that value. When you insert the smart card into a laundry machine
and start a cycle, the billing device in the machine (usually a drop-in
replacement for a coin acceptor with the same electrical interface) decrements
that value. And there you have it: the card is just like cash, representing
value on its own, with no online operations required.

Of course you can see the problems with this scheme: couldn’t anyone just write
a bigger number to the card? The earliest implementations tried to prevent this
with simple password schemes or very elementary cryptography, and results were
poor. The French payphone system of the late ’80s, for example, was known to be
vulnerable to duplication of cards and so naturally a black market emerged.

The history of early SVCs, mostly of the ’80s and ’90s, being vulnerable to at
least duplication if not outright forgery gave them a poor reputation for
security that persists to this day. It doesn’t need to be that way, though, and
excepting some obsolete systems still in use it isn’t. If we can make the
blockchain work we can certainly make SVCs work (admittedly this somewhat
self-defeating argument presages the failure of SVCs to catch on for general
purpose use). The problem with early SVC systems was the limited computational
capabilities of the smart card, no match for the high complexity of strong
cryptographic algorithms. Smart card technology advanced, though.

The term “smart card” is not very precisely defined but tends to refer to any
card with an Integrated Circuit Chip (ICC) compliant with one of several
specifications for physical and electrical interface, mostly ISO 7816 for
contact operation and ISO 14443 for contactless operation. It’s important to
understand that while the term “smart card” is most often used to refer to
contact operation, that’s not a limitation of the technology. Historically some
cards implemented contact and non-contact operation by having two separate
chips, but that method is well obsolete. Modern smart cards, especially payment
cards, are usually dual-interface cards where the same ICC is capable of
communicating the same logical protocol over either the contact interface
(“insert”) or the noncontact interface (“tap”). Since the noncontact interface
is compatible with NFC, smartphones are able to use their secure element to
run an application similar to the one that runs on EMV cards.

If these cards are so smart, what do they actually do? Well, that part has
varied a great deal over time. The earliest smartcards, developed in the ’70s,
were essentially memory and nothing else. Later on, though, smart card software
evolved to multi-application cards in which a smart card operating system
provides services and manages the selection of applications.

Perhaps the most famous smart card operating system is Java Card, a platform
that allows smartcards to run constrained Java applets. Java Card was developed
by French conglomerate Schlumberger, whose identity and card division spun out
to form a major part of Gemplus (now part of Thales). Besides supporting very
constrained devices, Java Card was designed for the high-security applications
typical of smart cards. It provides full-featured cryptography up to ECC on
modern devices, but more importantly enforces security isolation of applets
and their communications and memory.

Java Card is particularly widely known because of its role in the “Java Ring,”
a chunky fashion accessory that presents a Java Card environment in the
onewire-based “iButton” form factor. iButtons are a topic for their own post
one day, being surprisingly widely used in a couple of niches where their
improved durability over ICC-type smart cards is an advantage.

Java Card is also widely used, being one of the most common operating
environments on practical smart cards. There is a good chance that you have
more than one Java Card environment on your person at this moment. Discussing
the full scope of Java Card applications requires a bit more rambling on the
smart card as a physical object, though.

If you are a dweeb about identity documents, you have probably read into ISO
7810. This standard describes a set of physical form factors for identification
documents. Most notable is the ID-1 form factor, which is widely used for
payment cards, driver’s licenses, and in general any standard-sized wallet
card. Size ID-3 from the same standard is the norm for passports. But then
there’s an apparent oddity, size ID-000, a small 25x15mm card with a notch out
of one corner. Sound familiar? ISO 7810 ID-000 is the physical description
of a conventional SIM card.

SIM cards are just smart cards. Big reveal, I know! GSM was standardized by an
organization out of Paris in the same time period that France Telecom adopted
smart cards for payphone payment. When looking for a transportable means of
authenticating the phone owner, it was an obvious choice. SIM cards no longer
conform is ISO 7810 in most cases (having migrated to the smaller micro and
nano formats), but continue to be compliant with ISO 7816 for electrical and
protocol compatibility. It is no coincidence that SIM cards are often shipped
in an ISO 7810 ID-1 compliant carrier, since these make personalizing and
testing in the factory easy to do with standard smart card interfaces.

ISO 7816, the standard for smart cards specifically, describes the physical
position and layout of the contacts on the ICC. It also describes an electrical
interface [1] and logical protocol for communication with smart cards. Smart
card communication is based on APDUs, or application protocol data units,
packets exchanged between the reader and card. APDUs can indicate a
standardized cross-vendor operation code, or a proprietary operation specific
to some application on the card. This is a little network protocol used within
the confines of the card slot, and smart card applications specify which
APDU commands must be supported by cards.

The abstraction of the fairly well-defined APDU protocol creates a healthy
degree of separation between smart card uses and implementations. This is all
to say that the software running on smart cards often varies by vendor, even
within a common application. Java Card is very common, but not universal, for
both SIM cards and EMV payment cards. It competes with “native” operating
systems like MULTOS. These native operating systems tend to leave more memory
and processor time for applications because of the lack of a bytecode
interpreter (yes, Java Cards actually run a very constrained JVM), but usually
lead to application development in C which is less appealing than “weird
constrained Java” to many organizations.

As you might imagine given this range of applications, security expectations
for smart cards are high. In fact, the modern concept of a “secure element”
largely originates with smart cards, and many secure elements in things not
shaped even remotely like cards continue to use the ISO 7816 logical interface
and Java Card. The SIM card is really just a portable secure element, capable
of running multiple applications with nonvolatile storage, and in some
countries (mostly European) they have been used for broader identification and
authentication purposes. Smart cards are expected to be resistant to both
electronic and physical tampering. Smart cards were historically a common form
factor for cryptographic secure elements, being used to protect key material of
sensitivity ranging from satellite TV scramble codes to military communications
equipment—although for reasons of both durability and not having been
invented overseas, the US NSA has historically preferred more homegrown form
factors for cryptographic elements.

Putting this all together, you can probably see that it is indeed possible to
build a reasonably secure stored value smart card system. All increment and
decrement operations can be cryptographically authenticated. Unique secret
keys, “burned in” to cards as part of personalization and not readable from
outside of the secure element, can be used to authenticate the card and prevent
duplication. While it is conceptually possible to duplicate stored value cards
through laboratory analysis, the cost is unlikely to be less than the value cap
imposed by the SVC service.

In the ’90s, SVCs started to catch on. A marquee implementation went on display
to the world in 1996: at the Summer Olympics, held in Atlanta, three banks
partnered with the Olympic committee and businesses to offer an SVC payment
system. It was particularly appealing to international visitors: debit and
credit cards rarely worked overseas in 1996, and tourists in the US for the
duration of the Olympics could hardly be expected to open US bank accounts.
SVCs provided a convenient alternative to cash. Visitors could buy them in
fixed denominations with cash or travelers cheque, and value could be reloaded
at kiosks around the Olympics sites. The SVC nature of the system allowed the
offline payment terminals to be deployed to area businesses relatively cheaply,
without a requirement for a phone line like the credit card terminals of the
era.

The Olympics SVCs were manufactured by the usual suspects: Gemplus,
Schlumberger, and G+D. The cards ran a cryptographic application generally
based on the existing French payment card system, a precursor to EMV that was
focused on supporting offline use-cases. The Olympics experiment was mostly
considered a success, with few technical problems. The banks involved were
apparently underwhelmed at the number of cards issued, and it was speculated at
the time that they were perhaps more popular with collectors than users. One
can imagine that the SVC technology, entirely new to locals and visitors not
from Western Europe (and, to be fair, some from Australia), faced some
challenges in gaining consumer confidence.

SVCs became a standard feature of the Olympics for a few years, making their
last appearance (as far as I can tell) in 2002 at Salt Lake City. This was
reportedly a very limited system based on magnetic stripe cards, and so I
assume that it was not an SVC system at all but just a gift card system with
the heritage of the 1996 and 1998 SVCs. It is likely impossible to design
magstripe SVCs that are not vulnerable to trivial duplication, I know of only
one method and it is experimental (characterization of weak permanent magnetic
fields acquired by the magstripe during the manufacturing process, which seem
to be unique enough to differentiate individual cards).

SVCs saw other experimental applications at the same time. The University of
Michigan deployed a smart card SVC in 1996 as well, allowing students to load
funds and spend them on campus and at nearby businesses. This type of program
became fairly popular at large universities, but beware a terminological
challenge: many universities still refer to their student ID payment card
program as a stored value card for historic reason, but none that I’m aware
of today actually are. With universal acceptance of payment cards, it is far
more cost effective to make an arrangement with a bank and processor to encode
student IDs as Visa or MasterCard cards. They then function as specialty
prepaid cards with whitelisted merchants and purchase types, a service readily
available from the prepaid card issuance industry.

Another nascent application of SVCs in the US were welfare programs like SNAP
and WIC, implemented through a system called Electronic Benefits Transfer or
EBT (EBT replaced the physical “stamps” in “food stamps”). Once again, while a
few states adopted SVCs and may even still call their EBT cards SVCs, every
example that I know of today is processed on the Visa or MasterCard network as
a prepaid card.

Why is it that SVCs gained so little traction for payments in the US? A 1999
Spectrum article
rounds
up the state of SVCs at the time, optimistically opening that the contents of
your wallet “might be replaced by just two or three smartcards.” One look at
the typical wallet will show that this hasn’t gone as hoped. The true promise
of multi-application cards, that you could have your government ID, payment
card, health information, etc. all as applications on a single physical card,
is virtually nonexistent in practice. Outside of specialty systems like PIV,
the multi-application capability of smart cards is mostly only used to interact
with different kinds of payment networks. Perhaps the most common smart card
application in the US is called “CHASE VISA” and it is basically the reference
EMV application with the name changed [2]. If there’s even a single other
application on the card, it’s probably for interaction with an EFT network.

It’s fairly easy to see why this happened: different applications are issued
by different organizations. The thought of your driver’s license and credit
card being one physical object almost certainly induces nightmares of having
your credit card number stolen and then having to interact with the DMV (or,
as it is pronounced in the New Mexico vernacular, the MVD). The practical
logistics of multi-application cards are difficult to manage, and the cards
are cheap enough that it’s easier for everyone to keep different applications
separate.

What of payment cards, though? Smart cards for payments are now the norm even
in the backwards United States [3], but stored value systems are harder to find
today than they were in 1999. Spectrum elaborates, after discussing the
popularity of smart card systems (broadly defined) in Europe:

Why has it taken so much longer for smartcards to take off in the United
States? In the first place, some of these cultural and political drivers are
absent. The country has an excellent telecommunications infrastructure. There
is no governmental or centralized mandate in any of the traditional application
areas of smartcards. But the industry is evolving. The activities of Europay,
MasterCard, and Visa (EMV) in developing specifications for
financial-transaction cards will have a major impact on the U.S. market and the
rest of the world. Nonetheless, it is felt that a smartcard will have to be
able to handle several applications for the technology to gain widespread
acceptance in the United States.

EMV sure did have an impact in the US, even if it took a solid decade.
Multi-application cards seem dead in the water from a practical perspective;
even though many more sophisticated smart card systems (like MULTOS) are
designed for remote issuance and updating of applications. Anyone who has had
access to their office and email at the mercy of the USAccess/HSPD-12 PIV
scheme can attest that its Thales-built remote personalization system is…
not exactly ready for the average consumer.

Besides, the telecommunications point is not to be underestimated. By the time
SVC technology competed in America, telephone connected payment card terminals
were already becoming the norm (mostly from American Verifone, although French
Ingenico was a major player). Rates of telephone service and, not long after,
internet service in the US were very high. These factors made offline systems
much less attractive: merchants unhappy with the risk of offline processing of
non-chip credit cards were just moving to online processing, not to smart
cards.

The lack of a standards body to set the direction is also undeniably a factor.
The introduction of EMV took as long as it did in large part because of the
fragmentation of the payment card industry; different components of the market
had different objectives and there was no one to push them along. To be fair,
US payment card issuers cope with fraud better than most overseas observers
seem to give them credit for. The inconvenience of card fraud is relatively
low; I recently had credit card information stolen (how, I can only speculate)
and there was no action involved on my part beyond responding to a text message
alert and receiving a new card in the mail. Because of the card information
update service the processors provide to qualified merchants, I haven’t even
had to reenter my card information on any subscriptions. A lot of effort has
been put into smoothing over the fraud that occurs, even if it does seem that
one of my cards is used fraudulently every two years or so.

Despite the lackluster adoption of SVCs in the US, they have a few strongholds,
both here and abroad. First, although a somewhat minor detail, I cannot help
but note the military overseas SVC program that my career once incidentally
involved. The EagleCash system, operated by the Department of the Treasury,
provides SVCs to members of the armed forces (sometimes branded NavyCash or
Armed Forces EZPay due to variants of the program rules). The cards are mostly
used in overseas military installations and aboard ships, situations in which
offline processing can remain a big advantage. EagleCash was considered the
most prominent deployment of SVCs in the US, and probably still is. EagleCash
reaches nearly a billion dollars in annual turnover, mostly in the Middle East.

Much more widespread, though, are transit cards. Many transit systems globally
use some sort of SVC for fare payment, under different names in different
cities. Prominent US examples include Clipper (SF Bay area), Ventra (Chicago),
MetroCard (New York City), and SmarTrip (national capital region). Overseas,
Oyster (London), Rav-Kav (Israel), and Octopus (Hong Kong) are well-known. Many
of these systems were pioneering when implemented, and some remain pioneering
payments technologies today.

Many early US systems, such as Clipper, were implemented at least in part by
the Cubic Corporation. If that sounds like an ominous defense contractor, it
is. Cubic produces a wide range of C4ISR systems for the US military, but
because of its location (in the Bay Area) and early involvement in
transportation technologies, Cubic became a major US vendor in transit fare
collection systems. The nearly identical fare gates of BART and the DC Metro,
for example, were early models designed and built by Cubic (BART and DC Metro
are twin projects in many ways). They originally used magstripe tickets, and
I have read that they were controlled by PDP computers although I am unsure
if this factual or just confusion with the better documented use of PDP/8E
computers to drive the train arrival signs and announcements.

Cubic came back in the ’00s with noncontact SVC payment systems, which are now
widely deployed in major US cities and many overseas systems. Of the systems I
listed above, most had Cubic as at least a member of the consortium that
implemented them, if not as the prime contractor. Oyster, for example, was
implemented by Cubic alongside EDS, now a division of HP perhaps best
remembered for the political career of its founder Ross Perot.

How do these systems work exactly? Offline systems simplify payment networks in
some ways, but also add complexity, which is often apparent in transit systems
that combine offline terminals (for example in buses) and online terminals (for
example at train platforms). I will walk through a description of the operation
of Clipper, with which I am most familiar. The details vary from system to
system depending on architectural decisions made during the original system
design and modernization efforts that have been performed since, so details
vary. For example, some newer systems especially abandon offline operation
almost entirely and have even in-vehicle terminals perform online transactions
via either public or municipal LTE networks.

A Clipper card can be purchased from a number of vendors, either first-party
ticket windows in certain stations or private convenience stores that have
opted to participate in the program. These stores can also add value to an
existing Clipper card, from cash or a payment card transaction, by entering the
value to add into a device very much like a credit card terminal (it is,
running custom software as many do) and then tapping the card to it to allow
the write operation to complete. Similarly, cards can be purchased or value
added via vending machines at stations, which usually require the card to be
tapped twice: once to read the current value and determine eligibility to add
value (there is a value cap, for example), and a second time to write the added
value.

Because these transactions involve writing to the card, the new value is
available immediately. It can be spent on fixed terminals like station fare
gates, but also on vehicle terminals as in buses. Either way the terminal
reads the value from the card, determines eligibility, and writes the new
(decreased) value back to the card.

Things get a little bit strange, though, when you consider one of the most
common user patterns in the modern era: you can create an account online and
associate the card with your account, and then you can add value online. This
is convenient, but confronts the offline nature of the system. You add value
to the card, but there’s no way to write the new value to it.

The solution, or at least partial solution, to this problem looks something
like this: fare payment terminals have to receive a streaming log of value-add
operations so that they can apply them next they are presented with the
relevant card. Online systems, like vending machines and fare gates in train
stations, find out about online value-adds almost immediately. If you mostly
use a train, the operation is almost completely transparent, as you add value
online and it is written to your card next time you pass through a fare gate.
For the offline terminals in buses, though, things aren’t so smooth. These
terminals operate fully offline while the vehicle is on route. At the end of
the day, as vehicles are stored in yards, the payment terminals connect to a
local area wireless network (traditionally 802.11a). They upload on-vehicle
transaction logs for reporting, but also download logs of online transactions.
If you add value to a card with a zero (or near zero) value and then try to
board a bus, it is likely that you will be rejected: the value-add hasn’t been
written to the card yet, and the bus terminal hasn’t been told about it. The
transit operator often sets an expectation of one business day for online value
adds to be available if your first trip is an offline terminal If you add value
to a card with a zero (or near zero) value and then try to board a bus, it is
likely that you will be rejected: the value-add hasn’t been written to the card
yet, and the bus terminal hasn’t been told about it. The transit operator
often sets an expectation of one business day for online value adds to be
available if your first trip is an offline terminal.

It may be that Bay Area transit operators are transitioning to online vehicle
terminals to address this problem, it wouldn’t surprise me as IP connectivity
in transit vehicles is becoming the norm for multiple reasons. But, of course,
in an environment where all devices are online the value of SVCs as a
technology is greatly reduced. At some point the SVC nature of the system
becomes more vestigial than anything else, although it can provide valuable
fault tolerance.

The case of transit is more complex than just incrementing and decrementing,
though. Passes (including automatically “earned” passes in many systems) and
transfer discounts between operators can make fare logic surprisingly complex,
and that’s before considering the many rail systems that charge fare per zone
traveled. To accommodate this kind of fare tabulation logic, transit SVCs
typically store a history of the most recent transactions and cumulative
counters of different types of transactions. This allows the system to compute
distance-based fare (by comparing the current and previous transaction for
their location), offer transfer discounts (by comparing the last two or three
transactions to a table of discounts between operators), and automatically
change to passes when they become most economical (by checking registers of
accumulated fare per operator per time period).

Put together these programs can make fare calculation very complex, which is
one of the advantages of computerized fare collection with usage history: the
software can ensure that the fare paid is optimal, in the sense of being the
lowest fare the customer is eligible for. Prior to these systems features
like transfer discounts often went unused because of the added complexity of
presenting a ticket and payment or determining validation procedures between
transit agencies.

Even transit agencies are moving away from SVCs as IP connectivity to vehicles
becomes more affordable and more common. Centralized systems, while they
require network infrastructure, can be more flexible and more user-friendly.

It doesn’t look like SVCs have much of a future. Despite being the dream of the
’90s, they have gone the way of, well, so many other dreams of the ’90s
technology industry. By the time the ingredients for SVCs to succeed became
widely available, they were somewhat of a solution in search of a problem.
Network connectivity was spreading rapidly for other reasons, online processing
of payments offered other advantages, there just weren’t that many reasons to
go the SVC route.

Smart cards are an important part of payments infrastructure today because of
the EMV standard, and they continue to have applications in both their
traditional form factor and embedded variants. Despite the power available from
multi-application cards, MIFARE with its simple cryptographically protected
read/write operation is more common in practice. So pour one out for SVCs, or
more accurate to the tradition, put $10 on a laundry card, put it in a drawer,
and move to a different city.

[1] The topic of electrical interface is actually slightly confusing because
the standard describes 5v, 3v, and 1.8v logic levels. Modern cards are nearly
always 1.8v, but fully compliant readers need to detect and provide the correct
operating voltage to the card. This complexity is one of the factors that has
lead to occasional security vulnerabilities in smart cards around supply
voltage.

[2] Most payment card terminals query the name of the selected application and
display it. Often it is only “VISA” or “MASTERCARD” but a few issuers customize
their card loads to brand the application name. Just a bit of trivia.

[3] Outside of certain more niche applications like cardlock fuel cards,
which are broadly compatible with payment cards for ease of implementation but
don’t seem to be interested in making the move to chip-and-whatever.

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