Moving From Contactless to Wireless Technologies in Secure, Over-the-Air Transactions

Moving From Contactless
to Wireless Technologies
in Secure, Over-the-Air
Transactions

Moving From Contactless to Wireless Technologies

in Secure, Over-the-Air Transactions

The ability to process secure transactions over-the-air has transformed daily life.
From digital payments, border or premises controls, healthcare records, and even
transportation ticketing, over-the-air transactions are no longer a novelty but
an integral part of the daily interaction with the world. However, over-the-air
transaction services must continuously ensure the security of sensitive information,
while exploiting the use of secure technologies that protect user information from
real and potential threats.

Until now, contactless technology has been the most efficient and cost-effective
method for processing over-the-air transactions. Unfortunately, the small operating
range of the technology, typically just a few centimeters, is too restrictive for
many applications.

As a consequence, developers are increasingly turning to wireless technology as a
way of overcoming the limitations of contactless systems. Wireless devices not only
support an extended range of operation, but offer significantly enhanced system
capabilities. While wireless standards, such as WiFi and Bluetooth, are relatively
mature and provide a stable development environment for manufacturers, efforts
to address the use of wireless technology to process secure transactions are only
now emerging.

This UL white paper discusses some of the many issues and challenges that must
be addressed in the future deployment of wireless technology for the processing
of secure transactions. It begins with a discussion of the strengths and limitations
of both contactless and wireless technologies. The white paper then reviews
and assesses internal system risks, as well as external security concerns, for both
technologies. The paper concludes with some thoughts on the future use of wireless
technology in secure transactions, and how manufacturers can provide assurances
to both system providers and users regarding the security of their private data.

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“Contactless” vs. “Wireless” are significant impediments to efficient, minimize the risk of disclosing private

Today, contactless technology is the large-scale attacks. Nonetheless, the data and to prevent unauthorized access

method of choice for many secure communication channel itself represents to services. In addition, security has

transactions. A secure transaction a potential source of threats, since any become an important element for user

is composed of a secure operations individual with malicious intent can acceptance, since few users would utilize

sequence such as identification, secretly participate in a transaction WiFi connections if doing so routinely

authentication and encryption. These simply by locating themselves within exposed personal information to

operations routinely handle highly close proximity to a system. unauthorized parties.

sensitive information, such as secret Wireless technology, on the other hand, In an effort to address these concerns,
cryptographic keys or user-related means any technology connecting industry standards are being reviewed
personal data. Hardware secure standalone devices over the air using and revised to include additional
elements (HSM), such as smartcards, the 5GHz frequency band. This includes security requirements. For example,
are usually employed to process most of the wireless technologies that the 2007 Bluetooth v2.1 release
sensitive information securely are common in everyday life, such introduced significant improvements
and efficiently. as WiFi connections available with aimed at strengthening the wireless
computers and home automation communication pairing process. Similarly,
Contactless systems typically follow
systems utilizing Bluetooth or Zigbee- WiFi Protected Access II (WPA2) has
a “master/slave” communications
compliant communication protocols. replaced the original WiFi Protected
protocol. The master (usually a terminal)
These technologies all utilize the same Access (WPA) protocol and the Wired
is in charge of providing a carrier and
frequency band, and typically operate Equivalent Privacy (WEP) protocol to
controlling the transaction sequence.
within a range as large as 70 meters reinforce WiFi secure connections.
The carrier signal represents both a
indoors and up to 250 meters outdoors. However, questions remain as to
source of power for the HSM and a
whether the current wireless standards
communication vector. The slave (usually However, because of the wide operating
are suitable for meeting today’s
a smartcard) operates only upon request ranges available, wireless technology
more demanding concerns in secure
from the master, and is powered solely presents a unique set of risks for secure
over-the-air transactions.
by the terminal's carrier. The connection transactions. Attackers can position
interface usually provides a limited range themselves at a safe distance from Assessing System Risks
area, typically not more than a couple of legitimate communication activities
The total cost to ensure the security
centimeters. The HSM processes terminal and remain undetected. In addition,
of over-the-air transactions may be
requests in a secure manner, thereby since wireless devices remain active as
significant since the complexity involved
representing a key element in overall long as they are powered, their regular
in developing a completely secure system
system reliability and security. signal emission can be more easily
requires additional hardware resources
Over-the-air operation offers the detected and exploited.
and development time. However,
advantage of limiting harmful Initially, wireless technology was mainly it is possible to find an appropriate,
manipulation of the contactless device. devoted to the exchange of data between cost-effective solution by identifying
Unlike contact-based systems, a card two paired devices. However, many likely risks and determining an acceptable
holder in a contactless system is exempt wireless systems now afford one-to-many level of risk. Risk management relies on
from inserting the device in a reader, or many-to-many connections, a vulnerability analysis that identifies
thereby significantly reducing transaction strengthening the need for more secure potential threats in the context of the
duration. Further, since the range area is data exchanges. As such, authentication system’s actual use, and defines security
limited to a couple of centimeters, there requirements are now necessary to requirements to address those threats.

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A vulnerability analysis begins by creating an in-depth profile of a potential attack,
including the context within which an attack could occur and the possible motives of
an attacker. Then, a list of vulnerable assets or sensitive operations is drawn up. Once
potential threats and their targets are clearly identified it is possible to define minimum
security requirements and implement appropriate security measures. These measures
can include existing fraud techniques or by designing new approaches during the
system development process.

Confidentiality

Cryptographic keys are the heart of any secure system. Since their disclosure can
significantly compromise system security, preserving their confidentiality should be
the highest priority. But the need for confidentiality also extends to information and
other assets transmitted in over-the-air communications, since unauthorized parties
can intercept these data transfers. This is why secure WiFi data transfers are encrypted
in secured mode usage.

When addressing matters of confidentiality, it is necessary to distinguish between
private data processed internally from data exchanged through the communication
channel. Internally processed data, such as cryptographic keys, are typically subject to
physical attacks, and distant attacks are infrequently used to access such data. However,
private data accessible through the communication channel represents a potential
target and must be thoroughly protected.

Authentication

Authentication enables a system to restrict access to sensitive operations or data by
requiring the use of trusted data. For example, accessing a secure WiFi connection
typically requires the knowledge of a key or a pass phrase. As wireless and contactless
systems become more open, strong authentication requirements are essential to
eliminating illegal access to sensitive assets.

Privacy

Privacy becomes an issue when an unauthorized person successfully obtains personal
user information. The information disclosure does not directly affect a system security,
but it can be exploited to a user's detriment. By collecting some user's representative
data from a device, it becomes possible to identify or to track an individual user or
his/her habits. For instance, ePassport devices have been designed to withstand illegal
holder identifications, preventing anyone from accessing a authorized holder's name
or picture.

Over-the-air communications are especially vulnerable to privacy concerns, since there
is no physical restriction to prevent a transaction with a secure device. In such cases,
specific protections that combine strong authentication with high confidentiality are of
paramount importance. Users are likely to reject any technology solution that does not
offer the highest levels of privacy reliability.

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Data and Transaction Integrity Assessing External reasons, concealing rogue hardware to

A secure transaction relies on both a Security Risks catch contact-based transaction fraud is
defined sequence of operations and the Conducting a secure over-the-air not an easy task, especially since it must
exchange of data between different transaction potentially means that be operated at relatively close range.
devices. The security of a transaction can anyone is a prospective participant, However, for contactless or wireless
be compromised by either violating the either as a passive or an active player. devices, this technique becomes
sequence of commands, such as skipping An individual with malicious intent highly probable and can take place
an authentication step, or by modifying could then attempt to compromise the from a distance.
or tampering with the data exchange
security of a transaction in such a way The threat from eavesdropping is
itself. Communication integrity can only
that a fraud would go undetected by a already well-known in the wireless field.
be achieved through a combination of
user. The balance of this paper focuses Dedicated software, such as Wireshark
strong protocol design and a secure
on external threats, which are potentially or hardware sniffers for Zigbee, is readily
implementation. This is particularly
as damaging as those originating from available through the Internet, making
important for over-the-air channels,
system-based considerations. the potential for eavesdropping on
which are essentially unsecured.
Eavesdropping wireless communications fairly common.
Service Reliability
However, such easy access is not routinely
Incidents involving denial of services Over-the-air communication offers
available for contactless communications,
attacks have increased dramatically of anyone capable of intercepting a physical
which require possession and use of
late. The goal of such attacks is to create signal the opportunity to interpret it and
relatively specialized equipment for
a partial or a complete interruption of partially or fully retrieve any information
collecting and interpreting signals.
service, potentially compromising the being exchanged. This approach
considerably increases the distance from Data Corruption
security of a system or an operation
and providing an immediate gain for an which an attacker can operate when Data corruption consists of the insertion
attacker. Alternatively, a denial of service compared with the normal range area of or the modification of data exchanged
attack may represent an attempt to use. Obviously, the goal of eavesdropping during an official transaction. The goal
reveal a system’s underlying weakness, is to obtain access to the data being may be to change a normal transaction
undermining a user’s perception exchanged during a transaction. Even sequence, for example, skipping a
of security. a partial disclosure of data through this control or an authentication process. This
Service reliability is particularly important approach can potentially impact the attack technique has been successfully
for contactless and wireless devices, since privacy or confidentiality of the demonstrated on a contact-based chip
they are exposed to distant attacks. The user's data. and PIN product, in which the change
denial of service risk is particularly critical of a single byte led to the successful
Eavesdropping on a transaction in process
when devices can be compromised to completion of a payment transaction
is not a novel approach. For instance,
provide unauthorized access that can that bypassed the PIN verification result.2
contact-based banking cards may be
ultimately lead to the collapse of entire
subject to data disclosure when a secret For both contactless and wireless
systems. This is no longer a theoretical
possibility, as some industry researchers personal identification number (PIN) is technologies, inserting different data
have successfully inserted a self- transferred in plain text, justifying the use during a communication is not an obvious
replicating malware computer program, of a corresponding encrypted command. choice, since tampering directly with
i.e., a worm, into a local electric system The main difficulty lies in making an the physical signals of devices that are
using the wireless interface of a system’s attack transparent to a cardholder communicating in close proximity to one
smart meters. 1 or merchant. For obvious ergonomic another is neither easy nor realistic.

page 5


However, one way to overcome this and then proceed with an attack. An Skimming is only possible when the
challenge is to initiate a transaction attack from outside the vicinity of the attacker has the ability to communicate
by the use of relays. Relays are modules devices by means of relays is likely to directly with the device. For this reason,
whose function is to transfer data using escape detection. Therefore, as with data systems that allow distant access are
the same or a different channel. By using corruption, the risk level is correlated with particularly vulnerable to this form of
a relay, an attacker can artificially the operating range of the technology. attack. As a potential consequence, an
initiate a transaction between two individual with malicious intent may
Skimming
devices that would normally be too far obtain access to unprotected data, or may
apart to communicate with each other, Skimming is one of the most common challenge the security protocols with the
techniques for attacking a wireless intent of finding a breach.
thereby creating the opportunity to
corrupt the data using the system. Its aim is to initiate a fake However, as before, the operating range of
“man-in-the-middle” technique. 3 transaction without the consent of a the technology may be a factor in whether
device owner. As a result, private or skimming can occur. This is particularly
“Man-in-the-Middle”
sensitive information can be disclosed. true for contactless technology, the range
Another means of corrupting data is the Skimming can also be used to locate area of which is limited to a couple of
so-called “man-in-the-middle” technique, and subsequently exploit protocol centimeters. Expanding this range area is
in which an attacker positions a malicious weaknesses, such as authentication, and complicated, particularly when the radio
device in a genuine transaction between is an excellent method for initiating a frequency carrier must also supply power
two devices. To be effective, a malicious denial of service. to the device.
device must ensure that both devices
believe that they are connected with
each other, when they are in reality
communicating directly with a malicious
device alone. In this way, an attacker may
gain unauthorized access to confidential
information, or may be able to corrupt the
data being exchanged.

In a contactless or wireless context,
initiating a man-in-the-middle attack
in the vicinity of both devices is not a
simple process. Indeed, the malicious
device must first catch the attention
of each device in a one-to-one mode,
and then prevent them from directly
communicating with one another. In an
environment in which multiple devices
are operating in the same physical vicinity
and are receiving all communication,
a physical corruption of signals is unlikely.

A more realistic option would be to
take advantage of the communication
protocol to gain access to both devices

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Some researchers have investigated the maximum communications distances possible
with contactless devices. 4 It is interesting to note that the reading range of contactless
devices can reach one meter or slightly more using specific types of materials, compared
to a normal range area of a couple of centimeters. However, most research confirms
that an attack must take place in close proximity to a cardholder.

The distance limitation vanishes with wireless technology. The effect range area
expands to several meters, even dozens of meters, typically well within the distance
between two apartments in a building, for example. As a consequence, wireless
technology is particularly vulnerable to skimming, especially since the attacker can
remain hidden. Indeed, some software tools using this technique have been developed
to exploit weaknesses in WEP or WPA protocols of WiFi secure connections.

Side-Channels Attacks

To appropriately address security issues for sensitive applications, it is necessary to
remember that communication code is processed by hardware. Some attacks methods
have been developed that exploit the physical aspect of processing, defeating otherwise
robust specifications or designs. As a result, observation analyses may use hardware
to understand internal processing and potentially modify code execution, and may
result in the disclosure of confidential data through the analysis of inevitable
hardware leakages.

Since contactless devices are powered by a carrier supplied by a terminal, an attacker
can take advantage of this design to conduct side-channel attacks. Such attacks
monitor the device’s internal activity by analyzing the microscopic fluctuations on the
carrier signal. As a result, unprotected data may be disclosed using either simple or
statistical analyses. Cryptographic keys are particularly vulnerable to this kind of attack.5

Interestingly, this threat does not impact wireless systems, since power is supplied
directly to both devices, and the radio frequency signal serves only as a communication
vector. As a result, an attacker is not able to directly monitor power fluctuations or
remotely analyze internal processing. However, this does not mean that it is not worth
protecting devices against this kind of attack, since the risk still exists from attackers
who have physical access to a device.

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Conclusion
This white paper has illustrated some of the security challenges inherent in the
migration of secure transaction systems from contactless to wireless technologies.
Indeed, wireless technology introduces a range of distant attack techniques that can
compromise system security. Further, the attack profile is significantly different with
the use of wireless technology, since an attacker can safely remain at some distance
from targeted devices.

The emerging use of wireless technology for secure transactions means that any risk
assessment process must include an in-depth vulnerability analysis adapted to the
unique conditions presented by the technology. Such an analysis must include possible
threats, acceptable level of risk, and techniques in the protocol or device design that can
be used to mitigate any weaknesses.

The successful introduction of a secure transaction solution requires that both service
providers and users have high level of confidence that private or confidential data
will remain secure. Guarantees from a manufacturer of wireless devices can aid in the
development of the required confidence. Device certification by independent testing
laboratories supervised by competent authorities is also an essential element in
assuring both system operators and end users that important information will
remain protected.

Through its RFI Global Services, Ltd. subsidiary, UL has consulting and testing expertise
in wireless mobile communications, payment approval services, and wireless security
evaluations, the three primary areas involved in secure mobile payments.

For more information about the “Moving From Contactless to Wireless Technologies in
Secure, Over-the-Air Transactions” white paper, contact Jean-Luc Khaou, RFI Payments
and Security Manager at Jean-Luc.Khaou@uk.ul.com.

1
Davis, M. “Smart Grid Device Security: Adventures in a New Medium.” Presentation delivered at Black Hat USA, 2009. Web. 15 Jul 2011. http://www.ioactive.com/pdfs/SmartMeterBlackHat09Preso.pdf
2
Murdoch, S., Drimer, S., Anderson, R., Bond, M. “Chip and PIN is Broken.” IEEE Symposium on Security and Privacy, 2011. Web. 15 Jul 2011.
http://www.cl.cam.ac.uk/research/security/banking/nopin/oakland10chipbroken.pdf
3
The Computer Laboratory at the University of Cambridge has posted on its web site an interesting illustration of an attack using the relay technique, in which a presumably straightforward payment for
a sandwich is modified to pay for expensive jewelry, all without the cardholder’s knowledge. See Drimer, S. and Murdoch, S. “Chip & PIN (EMV) Relay Attacks.” Computer Laboratory. University of Cambridge,
2008. Web. 15 Jul 2011. http://www.cl.cam.ac.uk/research/security/banking/relay/
4
Koscher, K., Juels, A., Brajkovic, V., Kohno, T. “EPC RFID Tags in Security Applications: Passport Cards, Enhanced Drivers Licenses, and Beyond.” 16th ACM Conference on Computer and Communications Security,
2009. Web. 15 Jul 2011. http://www.cs.washington.edu/homes/yoshi/papers/RFID/ccs280-koscher.pdf
5
This technique has been adapted from the simple power analysis introduced in Kocher, P. “Timing Attacks on Implementations of Di e-Hellman, RSA, DSS, and Other Systems.” Dans Advances in Cryptology
CRYPTO 96, volume 1109 de Lecture Notes in Computer Science, pages 104-113. Springer. 1996.

©2011 Underwriters Laboratories Inc. All rights reserved. No part of this document may be copied or distributed without the prior
written consent of Underwriters Laboratories Inc. 9/11

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Moving From Contactless to Wireless Technologies in Secure, Over-the-Air Transactions

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