  In recent years, permissionless blockchains have gained significant attention
for their ability to secure and provide transparency in transactions. The
development of blockchain technology has shifted from cryptocurrency to
decentralized finance, benefiting millions of unbanked individuals, and serving
as the foundation of Web3, which aims to provide the next generation of the
internet with data ownership for users. The rise of NFTs has also helped
artists and creative workers to protect their intellectual property and reap
the benefits of their work. However, privacy risks associated with
permissionless blockchains have become a major concern for individuals and
institutions. The role of blockchain in the transition from Web2 to Web3 is
crucial, as it is rapidly evolving. As more individuals, institutions, and
organizations adopt this technology, it becomes increasingly important to
closely monitor the new risks associated with permissionless blockchains and
provide updated solutions to mitigate them. This paper endeavors to examine the
privacy risks inherent in permissionless blockchains, including Remote
Procedure Call (RPC) issues, Ethereum Name Service (ENS), miner extractable
value (MEV) bots, on-chain data analysis, data breaches, transaction linking,
transaction metadata, and others. The existing solutions to these privacy
risks, such as zero-knowledge proofs, ring signatures, Hyperledger Fabric, and
stealth addresses, shall be analyzed. Finally, suggestions for the future
improvement of privacy solutions in the permissionless blockchain space shall
be put forward.
