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This survey starts with a high-level overview of the technical workings of zero-knowledge proofs (ZKPs) with a focus on an increasingly relevant subset of ZKPs called zk-SNARKS. While there have been prior surveys on the algorithmic and theoretical aspects of ZKPs, our work is distinguished by providing a broader view of practical aspects and describing many recently-developed use cases of ZKPs across various domains. These application domains span blockchain privacy, scaling, storage, and interoperability, as well as non-blockchain applications like voting, authentication, timelocks, and machine learning. Aimed at both practitioners and researchers, the survey also covers foundational components and infrastructure such as zero-knowledge virtual machines (zkVM), domain-specific languages (DSLs), supporting libraries, frameworks, and protocols. We conclude with a discussion on future directions, positioning ZKPs as pivotal in the advancement of cryptographic practices and digital privacy across many applications.

"With a zero-knowledge proof (ZKP), a party can prove that a statement is true without revealing any information except for whether it is indeed true or not. The obvious benefit is privacy since the prover does not need to reveal any additional information, and the second benefit is that it can significantly reduce the cost of verifying the correctness of a statement. ZKPs are increasingly adopted in blockchain applications, where privacy and efficiency still have a lot of room for improvement. While it is expected that ZKP technology will also become ubiquitous in many other areas, the term remains cryptic to many people without a computer science background. In this review article, we shed light on what ZKPs are and how they improve privacy and efficiency and describe applications for blockchains and other use cases."

"zkp-ID enables companies to guarantee user's privacy while adhering to compliance requirements. In four easy steps a user is authenticated and checked against compliance parameters. After that a zero-knowledge proof (ZKP) - wrapped in a self-sovereign identity (SSI) credential - is decentrally stored in the user wallet."

"I'm going to argue that ZKPs are part of the blockchain shell game. Because blockchains have so many technical faults, ZKPs are touted as a solution - and the two together are so confusing it's easy to pass another complicated concept over our heads. Both are immature technologies where the perfect solution resides at some point in the future, and that's the ideal formula for more influencers to shill their bags. "

EY today announced the release of the third-generation zero-knowledge proof (ZKP) blockchain technology to the public domain on the Ethereum public blockchain. The enhancements of the ZKP blockchain technology will help make private transactions on public blockchains more scalable by significantly reducing transaction costs through batching multiple private transfers together in a single transaction.

The Bank of Korea (BOK) provided updates on its central bank digital currency (CBDC) proof-of-concept work in its 2022 Payment and Settlement Systems Report. This included investigating smart contracts, near-field communications (NFC) based offline payments and cross-border payments. Also, the BOK connected 14 banks with its simulated CBDC system to verify its functioning. It handled 2,000 transactions per second but slowed down as it reached capacity, so further improvements are needed. The bank also tested a zero-knowledge proof (ZKP) protocol to improve privacy, but it slowed the processing speed markedly. https://www.bok.or.kr/eng/bbs/B0000179/view.do?nttId=10078478&menuNo=400063

"What's ultimately so promising about ZKPs is that they have the potential to eliminate a major trade-off inherent in living, working, and transacting online: the convenience, speed, reach, and scale of the internet in exchange for our privacy. They also allow for nuance in a privacy landscape that's often black-and-white. "

"ZKProof promotes best practices for proper development and deployment of zero-knowledge proof (ZKP) systems, aligned with security and interoperability. The ZKProof Community Reference (ZkpComRef) intends to comprehend terminology, examples, explanations and recommendations, driven by research and experience. This serves as a reference from and for the community. The ZkpComRef is a live document. "

The Bank of Japan (BoJ) published a paper on privacy-enhancing CBDC technologies, comparing methods for privacy-preservation, such as homomorphic encryption and zero-knowledge proofs (ZKPs), and discusses how important other central banks rank privacy within their CBDC projects. As part of its CBDC research, the BoJ will continue to research and study privacy protection related to digital currencies with a wide range of stakeholders.

ZK-proofs still face challenges. They can't work in isolation. They still need to be attached to a truth source or "oracle." Doubts about computational complexity, usability and scalability remain as well.  But if these hurdles are surmounted, ZK-proofs could offer a 21st-century solution to not only the "fake news" challenge but also the privacy quandary as with CBDCs, providing just enough anonymity for users to comfortably use state-issued digital money but enough accountability so governments can be assured fraudsters or money launderers aren't infiltrating their networks.

"In this 2024 paper we propose, implement, and evaluate two extensions to OpenCBDC, an open-source transaction processor designed for central bank digital currency. First, we enable the central bank to audit the monetary supply. This feature reduces the trust required in sentinels - the most exposed components of this architecture - so that it can in principle be outsourced to intermediaries. Second, we leverage Pedersen commitments and zero-knowledge range proofs to hide transaction amounts while maintaining auditability. This feature improves privacy beyond the level offered by the original OpenCBDC design. Performance measurements show that auditability and privacy reduce the throughput of the shards to 30 % of the original, but the scalability remains close-to-linear in the number of shards. For example, 8 shards can process peak loads of ≈135,000 transactions per second. By adjusting resources, CBDC operators can meet their throughput goals with auditability and privacy."