zk-SNARKs: How much transformation can they bring?

Written by: 0xKira

Compiled by: Block unicorn

In the rapidly evolving landscape of cryptography and blockchain, few innovations have garnered as much attention as zero-knowledge (ZK) proofs. Once an obscure academic concept found only in theoretical computer science papers, zero-knowledge proofs have quickly transitioned from theory to mainnet, becoming a cornerstone of the next generation of cryptographic infrastructure.

The core of zero-knowledge proofs challenges a long-standing assumption in digital systems: verification requires the disclosure of information. Whether logging into an application, verifying identity, or confirming a transaction, we have always needed to disclose certain information in order to gain trust. Zero-knowledge proof technology breaks this trade-off, enabling us to prove facts about identity, data, or computation without revealing the underlying information.

In addition to privacy protection, zero-knowledge proofs can achieve scalability, interoperability, and trustless verification on a global scale. From ZK rollups that expand blockchain throughput to privacy-preserving identity and compliance systems, zero-knowledge proofs are redefining the possibilities in the crypto space.

Summary

Zero-knowledge (ZK) proofs can verify information such as identity, balance, or transaction validity without revealing the underlying data.

Although zero-knowledge proof technology was first proposed in the 1980s, it has only recently become practical due to advancements in computing, cryptography, and blockchain technology.

ZK proof supports private transactions, decentralized identity, DAO voting, and cross-chain interoperability, while scaling Ethereum by bundling thousands of transactions into a single proof through ZK Rollup.

Despite the large computational requirements, the ZK rollup algorithm offers instant finality, lower fees, and stronger security, making it superior to Optimistic-type solutions.

What is zero-knowledge proof?

Zero-Knowledge (ZK) proof is a cryptographic method that allows one party (the prover) to prove to another party (the verifier) that a statement is true, without revealing why the statement is true or any additional information.

For example, Alice wants to prove to Bob that she knows the password to a hidden door in the cave, but she cannot directly tell him the password. She enters the cave, opens the door, and then appears from the other side. Bob cannot see how she did it, but he knows she must know the password.

The classic metaphor of zero-knowledge proofs - Chainlink

Traditionally, verification requires the disclosure of certain information: such as identity information, passwords, or data. Zero-knowledge proofs disrupt this model by allowing one to prove identity, authenticity, or ownership without exposing the data itself.

In digital systems, this means you can:

Prove that you are over 18 years old without revealing your date of birth.

Prove sufficient funds without revealing wallet balance.

Proving the validity of a transaction without revealing its content.

This ability to “prove without revealing information” is the foundation of a system that maintains privacy, security, and transparency, and zero-knowledge proofs happen to balance these two characteristics.

How do they work?

Zero-knowledge proofs rely on intricate mathematical structures and cryptographic primitives, but conceptually, they can be distilled into three basic properties:

Completeness: If the statement is true, an honest prover can convince the verifier that it is true.

Soundness: If a statement is false, no cheating prover can convince a verifier to believe that the statement is false.

Zero-Knowledge: The verifier learns nothing other than the fact that the statement is true.

In fact, there are several types of zero-knowledge proofs, but the current focus of discussion is mainly on two types: interactive and non-interactive zero-knowledge proofs.

In early designs, zero-knowledge proofs were interactive. The prover and verifier engaged in a two-way dialogue, with the verifier posing random challenges and the prover providing responses as proofs, collaboratively building confidence in the truth of a statement. Although this model is theoretically effective, in a blockchain environment, parties often find it difficult to interact in real-time, leading to inefficiencies.

To make it more practical, cryptographers developed non-interactive zero-knowledge proofs (NIZK), which only require the prover to send a message to the verifier to complete the proof. The most famous of these is zk-SNARKs, which can generate extremely compact proofs and complete verification in milliseconds. Another variant is zk-STARKs, which does not require a trusted setup and provides post-quantum security levels.

How zk-SNARKs Work - Midnight Network

Essentially, these systems allow provers to generate a mathematical “fingerprint” of valid computations. Verifiers can then check this fingerprint without having to redo the entire computation. This is precisely why they are so powerful in blockchain scaling: by simply checking a single cryptographic proof, thousands of transactions can be quickly and cheaply verified.

When was zero-knowledge proof invented?

Zero-knowledge proofs can be traced back to the mid-1980s when researchers Shafi Goldwasser, Silvio Micali, and Charles Rackoff introduced the concept in their groundbreaking paper “The Knowledge Complexity of Interactive Proof Systems” (1985).

Their early theoretical models laid the foundation for decades of cryptographic innovation, but it wasn't until the 2010s, with improvements in computational efficiency and the rise of blockchain technology, that zero-knowledge proofs became practical.

Zcash and other projects were launched in 2016 and are among the first to deploy zero-knowledge proofs on a large scale. They use zk-SNARKs to enable private transactions on a public ledger. Since then, zero-knowledge proof technology has made significant advancements, with higher efficiency, faster proof generation, and the emergence of new frameworks (such as zk-STARKs, Halo, and PLONK) that make it easier for developers to use and more suitable for real-world system scalability.

What are the applications of zero-knowledge proofs in the field of cryptography?

The most intuitive and widely known application scenario is privacy-preserving transactions. Zero-knowledge proofs allow users to conduct transactions on a public blockchain without revealing sensitive information such as transaction amounts or counterparties. Zcash is a pioneer of this technology, introducing the “shielded transactions” mechanism, which protects user privacy while maintaining verifiable integrity on-chain. Building on this, projects like Tornado Cash, Aztec, and Railgun have extended zero-knowledge proof technology to Ethereum, enabling private smart contract interactions and confidential DeFi transactions.

How Tornado Cash Works - Elliptic

In addition to privacy protection, zero-knowledge proofs are revolutionizing the fields of digital identity and regulatory compliance. It supports selective disclosure, allowing users to prove specific facts about themselves without revealing personal data. For example, users can prove they have passed KYC verification without disclosing their name, or confirm that they are not on a sanctions list without providing identity information. This principle underlies emerging zero-knowledge identity systems such as Worldcoin's proof of personhood, Polygon ID, and zkPass.

Polygon ID: A identity system that supports zero-knowledge proofs - Polygon

Zero-knowledge proofs also have strong application value in voting and governance. In decentralized autonomous organizations (DAOs), they can facilitate anonymous yet verifiable voting processes, ensuring transparency of results while protecting the identity privacy of individual voters. This helps reduce the risk of coercion or retaliation, encouraging more honest participation in collective decision-making, thereby reinforcing the democratic principles of decentralized governance.

Another advantage of zero-knowledge proofs is reflected in the field of cross-chain verification. In a multi-chain environment, traditionally, establishing trust between different blockchains requires intermediaries or complex bridging mechanisms. Zero-knowledge proofs provide a more elegant solution: a proof generated on one chain can validate the state of that chain, while another chain can independently verify that proof. This achieves trustless interoperability, allowing different blockchains to communicate securely without relying on centralized validators.

ZK technology is also enhancing Ethereum's scalability through ZK Rollups. By bundling thousands of transactions into a single cryptographic proof, these Rollups significantly reduce on-chain data load while ensuring security. The result is faster transaction processing speeds, lower costs, and higher efficiency, laying the foundation for Ethereum to handle large-scale applications without compromising its decentralized characteristics.

ZK Rollup Explained

Among all applications based on zero-knowledge proofs, ZK rollups are undoubtedly the most transformative. They address one of the biggest challenges in the cryptocurrency space: the scalability of blockchains.

Since the birth of blockchain technology, all blockchains have faced the blockchain trilemma: that is, all blockchains can only achieve two out of the three core attributes of security, scalability, and decentralization. Blockchains like Ethereum, while secure and decentralized, are still very slow and expensive. Every transaction must be validated by all nodes, which creates bottlenecks, limits throughput, and drives up gas fees, severely reducing the usability of the blockchain.

Rollup is a Layer-2 solution that executes transactions off-chain and then publishes the summary information back to the main chain or Layer-1 (usually Ethereum). Rollup is mainly divided into two types: Optimistic rollup and ZK rollup.

In ZK Rollup, hundreds or thousands of off-chain transactions are bundled together. The prover generates a zero-knowledge proof (also known as a validity proof) indicating that all bundled transactions comply with the blockchain's rules. This single proof is then submitted to the main chain, which can quickly and conclusively verify it.

The Working Principle of ZK Rollup - Messari

This design significantly reduces the data volume and computational burden of Layer-1 while maintaining the same security guarantees as processing each transaction individually, thereby eliminating the speed and scalability bottlenecks of Layer-1.

Some representative projects of ZK rollup include:

zkSync Era: Developed by Matter Labs, it achieves fast finality using zk-SNARKs.

StarkNet: Built on zk-STARKs, emphasizing scalability and transparency.

Polygon zkEVM: A zero-knowledge implementation of the Ethereum Virtual Machine (EVM), enabling full compatibility with existing smart contracts on Ethereum.

Lighter: A perpetual DEX platform built on a custom ZK rollup, utilizing zk-SNARKs, specifically Plonky2.

Advantages of ZK Rollup

By compressing thousands of transactions into a single cryptographic proof, ZK rollups can significantly increase throughput, allowing blockchains like Ethereum to handle more activity without sacrificing decentralization or security.

Security is another key advantage. Unlike Optimistic rollup, which relies on economic incentives and a one-week challenge period to detect fraud, ZK rollup uses mathematical validity proofs to guarantee correctness in advance. Once the proof is verified on-chain, the underlying transactions are final and immutable, eliminating delays and uncertainties.

This also means faster confirmation speeds. Transactions in ZK rollups are settled immediately after their corresponding proofs are verified, allowing users to obtain final results almost instantly compared to the waiting times commonly found in Optimistic systems.

Cost-effectiveness is another major advantage. Since ZK Rollups submit only a minimal amount of data to the Layer-1 blockchain, Gas fees are significantly reduced, making it cheaper for users and applications to operate on Ethereum.

Even more exciting is that ZK rollup opens the door to enhanced privacy protection. Since it is built on zero-knowledge cryptography, it can theoretically embed confidentiality directly into the rollup itself, enabling large-scale private and verifiable transactions.

The main limitation at present is the computational demands. Generating zero-knowledge proofs still requires a significant amount of resources, necessitating powerful hardware and advanced cryptographic techniques. However, ongoing advancements, particularly in hardware acceleration, circuit design, and recursive proofs, are steadily reducing these costs, making each generation of ZK rollups more efficient.

Comparison with Optimistic Rollup

Optimistic rollups, such as Arbitrum and Optimism, follow a different philosophy. They assume by default that all off-chain transactions are valid. Only when someone challenges this assumption does the system require “fraud proofs” to verify disputes, a process that usually takes about a week. This model works well in practice but can cause delays in the final confirmation of transactions and relies on incentive mechanisms to encourage participants to identify and report invalid activities.

ZK rollup attaches a zero-knowledge validity proof to each batch of transactions, mathematically confirming their correctness before being written to the main chain, thus providing instant finality and stronger security guarantees, but it also brings higher technical complexity and greater computational load.

Essentially, these two models represent different trade-offs. Optimistic Rollup is easier to implement and currently dominates the Layer-2 space on Ethereum due to its simplicity and full compatibility with the Ethereum Virtual Machine (EVM). ZK Rollup is more complex, requires more computation, but offers faster settlement speeds, lower costs, and the potential for built-in privacy.

Conclusion

Zero-knowledge proofs represent a paradigm shift in how we trust, maintain privacy, and verify within digital systems. This concept, originating from abstract cryptographic theories in the 1980s, has now become one of the most promising technologies driving the development of the next generation of decentralized infrastructure.

In the cryptocurrency field, zero-knowledge proofs support private transactions, decentralized identity, cross-chain interoperability, and most importantly, scalable rollup architectures that can significantly increase throughput while maintaining Ethereum-level security. Their applications also extend beyond blockchain, expanding into finance, artificial intelligence, and data validation.

Although the application of zero-knowledge proofs is still at a relatively early stage, its development trajectory is already clear. Zero-knowledge proofs are shifting from a novelty technology in the field of cryptography to an essential component of infrastructure development. If blockchain is to scale to billions of users while ensuring privacy and decentralization, then zero-knowledge proofs are likely to be the key to unlocking that future.