Vulnerability Is Discovered in Security for Smart
Cards
By JOHN MARKOFF
AN FRANCISCO, May 12 � Two University of Cambridge
computer security researchers plan to describe on
Monday an ingenious and inexpensive attack that
employs a $30 camera flashgun and a microscope to
extract secret information contained in widely used
smart cards.
The newly discovered vulnerability is reason for
alarm, the researchers said, because it could make it
cost-effective for a criminal to steal information
from the cards.
Smart cards are used for dozens of different
applications, including electronic identity
protection, credit and debit cards and cellular phone
payment and identity systems.
The Cambridge researchers said they had discussed
their discovery with a number of card manufacturers,
and several had acknowledged the vulnerability. One
company reported that its security testing teams had
already considered types of attacks similar to the one
mounted by the Cambridge team and that they believed
their products were not vulnerable.
The researchers said they had also proposed a
potential design change to the companies that would
protect against the attack.
"This vulnerability may pose a big problem for the
industry," they wrote in their paper, "Optical Fault
Induction Attacks." The researchers argued the
industry would need to add countermeasures to the
cards to increase their security.
The Cambridge group's discovery is one of two new
smart card attacks that will be introduced Monday
evening in Oakland, Calif., at an Institute of
Electrical and Electronics Engineers symposium on
security and privacy.
A team of researchers from I.B.M.'s Thomas J. Watson
Laboratory in Yorktown Heights, N.Y., said they would
present a report at the conference based on their
discovery of a different vulnerability in subscriber
identification module, or S.I.M., cards. These are
used in the type of digital cellphone known as G.S.M.,
widely used in Europe and to a lesser extent here.
The vulnerability would make it possible for a
criminal to find the secret information stored in the
card, steal the user's cellphone identity and make
free phone calls.
Smart cards are credit-card-like devices containing a
microprocessor chip and a small amount of computer
memory for storing bits of electronic data that
represent money or other information that can be used
to ensure identity, like a code or a digitized retina
scan or fingerprint.
More widely used in Europe than in the United States,
the cards have long been promoted as the key to a
cashless society as well as for identity and
authorization applications. Some countries have begun
using them for national identity cards, and they have
recently been discussed as a way of confirming
travelers' identities to speed airport security.
The Pentagon has armed soldiers with smart cards for
online identity and physical access, and the cards are
in use in the United States in commercial services
like the American Express Blue credit card and the
Providian Smart Visa Card. Both cards are offered by
their providers as a convenient and safe way to make
Internet purchases, although their actual use for
those purposes so far has been limited.
Some of the information stored in the card is in the
form of a number composed of ones and zeros that
cryptographers refer to as a "private key." That key
is part of a two-key system that is used to encode and
decode information. The security of such systems is
compromised if the private key is revealed.
Typically, after the card holder authenticates the
card by supplying a pin number, the private key will
then be used to encrypt any sort of transaction using
the card. For example, the card might be used to
authorize a purchase or a transfer of funds, make an
e-mail message private, log on to a computer network
or enter a building.
The researchers from Britain, Sergei Skorobogatov and
Ross Anderson, who are based at the University of
Cambridge Computer Laboratory, discovered the flaw
after Mr. Skorobogatov found that he could interrupt
the operation of the smart card's microprocessor
simply by exposing it to an electronic camera
flashbulb.
They were able to expose the circuit to the light by
scraping most of the protective coating from the
surface of the microprocessor circuit that is embedded
in each smart card.
With more study, the researchers were able to focus
the flash on individual transistors within the chip by
beaming the flash through a standard laboratory
microscope.
"We used duct tape to fix the photoflash lamp on the
video port of a Wentworth Labs MP-901 manual probing
station," they wrote in their paper.
By sequentially changing the values of the transistors
used to store information, they were able to "reverse
engineer" the memory address map, allowing them to
extract the secret information contained in the smart
card.
Mr. Skorobogatov is a Russian emigrant who was once
employed in the former Soviet Union's nuclear weapons
program, where his job was to maintain bombs.
Mr. Anderson is a well-known computer security
researcher whose work in both computer security and
cryptography is widely recognized.
The researchers said they had discussed their findings
with a number of companies that had acknowledged the
vulnerability. However, at least one manufacturer who
had read the paper said it believed its products were
not vulnerable to the attack.
"This is a paper for an academic conference," said
Alex Giakoumis, director of product lines for the
Atmel Corporation, a San Jose, Calif.-based maker of
smart cards. "We've already looked at this area."
He said his company had built defensive measures into
its products that would make them invulnerable to such
an attack. However, he said he was unwilling to be
specific about the nature of the security system,
because such information would be valuable to someone
who was attempting to break the security of the Atmel
smart cards.
The I.B.M. paper, which is titled "Partitioning
Attacks: Or How to Rapidly Clone Some G.S.M. Cards,"
was prepared by Josyula R. Rao, Pankaj Rohatgi, Helmut
Scherzer and Stefan Tinguely.
The researchers reported that they had dramatically
shortened the time needed to steal secret information
from today's G.S.M. cellphones.
Their new approach can seize the information within
minutes, they said, making it a much more useful
method than either breaking the cryptographic
algorithms used by the card or by intrusive attacks
such as the Cambridge approach. The I.B.M.
researchers' report also offers advice to the smart
card industry on how to protect against
vulnerabilities.
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