IEEE Solid-States Circuits Magazine - Fall 2020 - 76

To harm the performance of critical tasks
performed by IoT devices, an adversary can
exploit this wireless charging capability by
counterfeiting the charger.
accepting power or if the power from
the charger should be blocked. This
is done by shifting the resonant fre-
quency of the IoT device vis-à-vis the
charger without using any switched
passives. Instead, two coils with con-
figurable coupling are used: a main
coil for receiving power during the
tuned case and an auxiliary coil for
adjusting the detuning amount of
the receiver. Furthermore, this work
can also ensure equal power delivery
using the same detuning technique
when there are multiple receivers
with heavily skewed coupling to the
same charger.

Secure Packageless THz
Identification Tags
RF identification (RFID) tags have
been widely utilized in supply-chain
management and authentication of
products [29]. However, in current
solutions, their size and cost are
limited by packaging and their ex-
ternal antenna requirements. There
is an urgent need for low-cost sub-

millimeter or even particle-sized
tags that can be embedded on every
small and inexpensive industrial
or medical component to provide
authentication. This work aims to
achieve this wide deployment of the
cryptographic passive IDs for ubiq-
uitous tagging. For example, one tar-
geted area is developing technology
against pharmaceutical fraud. Coun-
terfeit medicines [30] account for 10%
of the global medicine trade. Current
approaches include holograms and
color-shift inks, but they can be eas-
ily duplicated. Alternatively, RFIDs
are also used, but their cost is still
too high. More importantly, these au-
thentication tags are mostly on the
medicine package due to the large
size, making it easy to illegally reuse
or refill the packages. Detection of
counterfeit IC chips is another criti-
cal application especially impacting
the economy of the semiconductor
industry. Most counterfeited chips
come from recycling. An embedded
ID with encrypted, immutable data

THz ID

tracking the production and trade
history of the chip greatly reduces
the possibility of recycling. Further-
more, the monolithic integration
feature of a tag with the CMOS chip
but without requiring any packaging
or off-chip antennas can reduce the
additional cost for authentication
and make tampering too costly for
the adversary. The tangible applica-
tions of these particle-sized ID tags
can be extended to counterfeiting
banknotes, tooth implants, and au-
tomotive and aircraft parts. Recent
hardware prototypes [31]-[35] de-
veloped to address the challenge of
secure pervasive tagging of every
object have been limited by their
size, energy consumption, or secu-
rity limitations. In this example [36],
researchers present a packageless
and monolithic THz tag chip, seen
in Figure 15, with an embedded, lowpower, compact ECC processor. The
public-key authentication protocol
implemented in the THz tag chip is a
private ID scheme with three funda-
mental characteristics: correctness,
soundness, and privacy [37], [38]. To
establish the security of the ID pro-
tocol, correctness and soundness
are required, while privacy ensures
that no adversary can eavesdrop on
any information regarding the tag's
identity from the protocol m
- essages.

Sesame
Seed

Commercial RFID

FIGURE 15: A tiny package-less THz ID tag with an embedded public-key cryptographic processor for authentication [36].

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