  Design approaches based on certified hardware have featured prominently in
the recent debate concerning the deployment of large-scale digital currency
systems in general and systems to support central bank digital currency (CBDC)
in particular. Certified hardware is a cornerstone of the so-called "trusted
computing" paradigm, wherein a user carries a device designed to operate in a
manner that respects the will of a third party in preference to the will of the
user. The justification for such approaches is usually given in terms of the
perceived need to facilitate offline payments or to facilitate the recovery of
lost assets. In this article, we critically assess the essential problems that
digital currency solutions are being proposed to solve, particularly with
respect to the future of payments and the future of cash. Next, we examine the
characteristics of trusted computing within the context of its application to
digital currency systems and its potential impact on the power relationships
between the users of devices, the manufacturers of devices, and other powerful
actors such as corporations and the state. Finally, we assess the validity of
common justifications for certified hardware in the context of alternative
designs, limitations, and trade-offs. We conclude that the interests of
consumers would be better served by design approaches to digital currency that
do not require the use of trusted hardware.
