  Modern societies have adopted government-issued fiat currencies many of which
exist today mainly in the form of digits in credit and bank accounts. Fiat
currencies are controlled by central banks for economic stimulation and
stabilization. Boom-and-bust cycles are created. The volatility of the cycle
has become increasingly extreme. Social inequality due to the concentration of
wealth is prevalent worldwide. As such, restoring sound money, which provides
stored value over time, has become a pressing issue. Currently,
cryptocurrencies such as Bitcoin are in their infancy and may someday qualify
as sound money. Bitcoin today is considered as a digital asset for storing
value. But Bitcoin has problems. The first issue of the current Bitcoin network
is its high energy consumption consensus mechanism. The second is the
cryptographic primitives which are unsafe against post-quantum (PQ) attacks. We
aim to propose Green Bitcoin which addresses both issues. To save energy in
consensus mechanism, we introduce a post-quantum secure (self-election)
verifiable coin-toss function and novel PQ secure proof-of-computation
primitives. It is expected to reduce the rate of energy consumption more than
90 percent of the current Bitcoin network. The elliptic curve cryptography will
be replaced with PQ-safe versions. The Green Bitcoin protocol will help Bitcoin
evolve into a post-quantum secure network.
