Over the past five years, the rewards associated with mining Proof-of-Work
blockchains have increased substantially. As a result, miners are heavily
incentivized to design and utilize Application Specific Integrated Circuits
(ASICs) that can compute hashes far more efficiently than existing general
purpose hardware. Currently, it is difficult for most users to purchase and
operate ASICs due to pricing and availability constraints, resulting in a
relatively small number of miners with respect to total user base for most
popular cryptocurrencies. In this work, we aim to invert the problem of ASIC
development by constructing a Proof-of-Work function for which an existing
general purpose processor (GPP, such as an x86 IC) is already an optimized
ASIC. In doing so, we will ensure that any would-be miner either already owns
an ASIC for the Proof-of-Work system they wish to participate in or can attain
one at a competitive price with relative ease. In order to achieve this, we
present HashCore, a Proof-of-Work function composed of "widgets" generated
pseudo-randomly at runtime that each execute a sequence of general purpose
processor instructions designed to stress the computational resources of such a
GPP. The widgets will be modeled after workloads that GPPs have been optimized
for, for example, the SPEC CPU 2017 benchmark suite for x86 ICs, in a technique
we refer to as inverted benchmarking. We provide a proof that HashCore is
collision-resistant regardless of how the widgets are implemented. We observe
that GPP designers/developers essentially create an ASIC for benchmarks such as
SPEC CPU 2017. By modeling HashCore after such benchmarks, we create a
Proof-of-Work function that can be run most efficiently on a GPP, resulting in
a more accessible, competitive, and balanced mining market