IEEE Circuits and Systems Magazine - Q3 2021 - 20

Electromagnetic (EM) attack measures the electromagnetic signals from
cryptographic devices and retrieves the secret key information.
ii. Electromagnetic Attack Countermeasures
Electromagnetic (EM) attack measures the electromagnetic
signals from cryptographic devices and retrieves
the secret key information [121]. EM attack is the major
side-channel attack as it can be performed without the
direct access of IC/system [122]. Moreover, EM attacks
can succeed with lower computation data compared to
power side-channel attacks [123]. Several CMOS based
countermeasures like modifying crypto engine architecture,
power management circuits, and design flow of the
IC have been proposed to prevent EM SCA attacks [121]-
[125]. A countermeasure based on randomizing the assignment
of sensitive data to the set of AES S-boxes is
proposed that enhances the security against localized
EM attacks [121]. A popular method has been developed
that exploits on-chip voltage regulators [119]. Several
countermeasures have been proposed using inductive
integrated voltage regulators that isolate and modify
the EM signals of the encryption engine [123]. An EM
equalizer that flattens the EM profile is also proposed
by adjusting the on-chip power grid impedance [124].
Signature attenuation embedded crypto with low-level
metal routing uses lower metal layers for routing to suppress
critical EM radiation [125].
Besides, from this survey, it is identified that none
of the works have performed EM attacks on emerging
device technologies. Lack of fabrication facilities, EDA
tools, and resources related to emerging devices might
be the strong reason behind this. A complete EM attack
analysis needs to be performed to know the EM signals
emission rate and robustness of the emerging semiconductor
devices and memory technologies. As emerging
technologies have shown several superior characteristics
for hardware security, they may provide high robustness
and simpler solutions. Moreover, it is a good
opportunity for the researchers to explore the EM attacks
on emerging technologies.
iii. Photonic Attack Countermeasures
Photonic emission analysis (PEA) is considered a powerful
side-channel analysis due to its selective in-depth
analysis on specific parts of the hardware [126]. Thus,
side-channel attacks targeting a single transistor inside
the IC have become reality [126]. Furthermore, considering
the specific hardware areas instead of the entire
IC results in better signal-to-noise ratios [127]. In CMOS
technology, carriers generate photons due to high
electric field at the drain side. PEA allows the adversary
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to monitor the transistors from the IC backside (through
the substrate) by exploiting the transparency of silicon
to near-infrared light [27]. Earlier, it has been proved
that the hot-carrier luminescence generated from CMOS
logic is data and computations dependent [128]. Later,
a simple PEA has demonstrated on CMOS based AES
cryptographic engine and the secret key is successfully
recovered [128].
In the recent past, many countermeasures have been
demonstrated to enhance the security of CMOS IC designs
against optical analysis [126]-[128]. A method of
adding an opaque layer has been demonstrated to protect
the backside of the chip from optical attacks [126].
However, adversary or untrusted foundry can remove
such layers by the polishing mechanism. A backside
polishing detector is also proposed to monitor the
thickness of bulk silicon (substrate) [127]. Apart from
this, light sensors are also used to identify laser simulations
on the chip [128]. The drawback of this method
is that the light sensors detect laser signal with energy
lower than silicon bandgap. Due to the unavoidable
challenges and diversity of PEA, a one-stop solution
is still not demonstrated for IC protection. Contrary
to CMOS technology, emerging devices show high resilience
towards photonic attacks. Recent research
revealed that spintronic based GSHE switches do not
exhibit photon emission due to their magnetic switching
principle [129]. As a result, the systems based on
these devices inherently show high robustness against
photonic attacks. Graphene photodetector and CNT
optical sensors have shown high sensitivity towards
optical and near-infrared signals due to their excellent
material properties [130]-[131]. Consequently, these
sensor acts as security components in ICs and alerts
while performing photonic attacks. Finally, Table 5
presents a comparison of the different SCA attacks. It
can be observed that several emerging devices have
been explored to counter power analysis attacks. Apart
from the hazardous nature, researchers still have not
fully explored emerging device technologies against
EM and photonic attacks.
C. Hardware Obfuscation
Security of ICs in modern product life cycle management
has become a serious issue due to threats such as
counterfeiting, unauthorized overproduction, reverse
engineering, and malicious circuit insertion [11], [132],
[133]. The semiconductor manufacturing companies
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