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@ -201,6 +201,13 @@ basic construction and layout has not changed much since the early 1990ies~\cite
macphersonImprovementsSecurityEnclosures1993,
macphersonTamperRespondentEnclosure1999}.
Concluding this brief history of tamper sensing meshes, we find that they were initially developed for sensitive
military applications, and their use in civil applications is a recent phenomenon. The implementation of tamper sensing
meshes in civil applications was likely catalyzed by two advancements in electronics. First, electronic components
became less expensive and more integrated reducing the cost overhead of tamper sensing circuits. Second, the mass-scale
adoption of PCB and FPC production processes enabled their use as inexpensive, high-resolution substrates for such
meshes.
\subsection{Monitoring Circuit Approaches}
Tamper sensing meshes are most effective when they are continuously monitored using a backup power supply while the rest
@ -230,23 +237,21 @@ in early tamper sensing mesh implementations~\cite{
Besides tamper sensing meshes, environmental sensors such as temperature or light sensors are frequently used as a
secondary line of defence in HSMs and similar devices. By placing such sensors in the device and verifying the device is
within its nominal operating environment, tampering can be made less convenient. Modern security standards often mandate
the implementation of at least a temperature sensor to prevent cold-boot attacks on a device. A multitude of other
sensors have been proposed, including humidity sensors, vibration sensors, light sensors, magnetometers, and radiation
sensors such as X-ray sensors have been proposed. While the implementation cost of most sensor types is low, each
additional environmental sensor comes with an increased false alarm rate.
% FIXME citations?
the implementation of at least a temperature sensor to prevent cold-boot attacks on a device~\cite{
usnationalinstituteofstandardsandtechnologySecurityRequirementsCryptographic2019,
ISOIEC19790}.
A multitude of other sensors have been proposed, including vibration sensors, light sensors,
magnetometers, and radiation sensors such as X-ray sensors have been proposed. While the implementation cost of most
sensor types is low, each additional environmental sensor comes with an increased false alarm
rate~\cite{andersonSecurityEngineeringGuide2020}.
\section{A Survey of Meshes in the Wild}
Concluding the brief history of tamper sensing meshes above, we find that they were initially developed for sensitive
military applications, and their use in civil applications is a recent phenomenon. The implementation of tamper sensing
meshes in civil applications was likely catalyzed by two advancements in electronics. First, electronic components
became less expensive and more integrated reducing the cost overhead of tamper sensing circuits. Second, the mass-scale
adoption of PCB and FPC production processes enabled their use as inexpensive, high-resolution substrates for such
meshes. In this section, we will examine a large sample of recent devices that include tamper sensing meshes to gain an
In this section, we will examine a large sample of recent devices that include tamper sensing meshes to gain an
understanding of how they are implemented, and what security level they are targeted towards. Since we were unable to
acquire a nuclear weapon for our research, we limited our survey to commercial devices with a focus on card payment
terminals, which represent the most varied class of device incorporating such meshes.
acquire a nuclear weapon for our research, we limited our survey to commercial devices. While we analyzed devices across
a broad spectrum of applications, our survey includes a large variety of card payment terminals, which represent the
most varied class of device incorporating such meshes.
\subsection{Specimen Selection}
@ -374,19 +379,19 @@ terminals are cost-sensitive devices, which is reflected in the construction of
When credit card payments are handled on the web as opposed to in a physical store, HSMs are used in data centers to
handle plaintext payment data such as credit card numbers. Such HSM appliances are usually standalone rackmount devices
and are used across application domains. Depending on the application, these HSMs can be programmed with custom code, or
can be used as coprocessors through an API. In practice, the standalone appliances are just low-end computers in a
rackmount enclosure that expose the API of an internal HSM add-in card to the network. In this survey, we obtained two
devices labelled as HSMs. We were only able to procure two such devices since they are expensive, and even used
specimens of older models are usually listed for several hundreds to several thousands of Euro. Unfortunately, one of
the devices we obtained did not contain any security meshes in its case, and thus would not provide adequate protection
against advanced attacks. The other specimen we procured was a 2011 model Utimaco CryptoServer LAN. Our unit was a
white-label variant procured by premium TV encryption technology provider Irdeto, presumably used in Germany to produce
cryptographic key streams for TV signal encryption. We bought the device from a recycling company specialized on
datacenter components. The device was sold with any HDDs removed. The device consisted of an older mainboard for
embedded applications containing an Intel Core 2 Duo-brand processor and 2 GiB of DDR2 RAM, which was connected to the
HSM add-in card through PCI. The device contained a small Lithium backup battery on the add-in card, and another, larger
battery in an enclosure at the front of the device that was connected to the card through a cable. The device did not
contain any obvious case intrusion sensors.
can be used as coprocessors through an API~\cite{LunaNetworkHSM}. In practice, the standalone appliances are just
low-end computers in a rackmount enclosure that expose the API of an internal HSM add-in card to the network. In this
survey, we obtained two devices labelled as HSMs. We were only able to procure two such devices since they are
expensive, and we found that even used specimens of older models are usually listed for several hundreds to several
thousands of Euro. Unfortunately, one of the devices we obtained did not contain any security meshes in its case, and
thus would not provide adequate protection against advanced attacks. The other specimen we procured was a 2011 model
Utimaco CryptoServer LAN. Our unit was a white-label variant procured by premium TV encryption technology provider
Irdeto, presumably used in Germany to produce cryptographic key streams for TV signal encryption. We bought the device
from a recycling company specialized on datacenter components. The device was sold with any HDDs removed. The device
consisted of an older mainboard for embedded applications containing an Intel Core 2 Duo-brand processor and 2 GiB of
DDR2 RAM, which was connected to the HSM add-in card through PCI. The device contained a small Lithium backup battery on
the add-in card, and another, larger battery in an enclosure at the front of the device that was connected to the card
through a cable. The device did not contain any obvious case intrusion sensors.
\subsubsection{ATM Encrypting Pin Pads}