Zero-knowledge proves allow one party to show another a truthful statement without divulging any additional information. The cryptographic technology behind blockchain privacy is scalable rollups and an increasing number of identity authentication systems.
The following is a summary of the information that you will find on this page.
- The zero-knowledge method allows a proponent to prove that the computation performed was correct without having to reveal any data. This improves both privacy and scaleability of blockchains.
- The main zero-knowledge-proof families used by blockchain include zk SNARKs (which require a trusted initial setup) and zk STARKs (which do not require a trusted initial setup, but provide larger proofs).
- Ethereum layer-2 rollups, such as zkSync and Scroll, or Polygon zkEVM, use zero-knowledge to reduce thousands of transactions down into a verified proof on the mainchain, reducing gas cost by up to 90%.
- Vitalik Buterin released the GKR protocol late in 2025, as a means to accelerate Ethereum proof-of-zero knowledge verification. The goal was to make it practical to use on a daily basis.
- The mathematical foundations of zero-knowledgeproofs is solid, but it’s not magical. The proofs depend on certain cryptographic assumptions.
A cave analogy is used to explain zero-knowledge. Ali Baba is aware of the code word that opens a cave door. The word can be proved by him entering the cave and leaving it from the opposite side on command, but without saying anything out loud. The verifier can be statistically sure that Ali Baba is the mastermind after a number of successful demonstrations.
It is correct, but it’s incomplete. This analogy is correct but incomplete. It is not caves and doors that are the focus of zero-knowledgeproofs. It is about polynomial committments, elliptic curvature pairings and mathematical properties which allow one party encode a computation in terms of a series of constraints, while another can verify whether those constraints have been satisfied.
In this article, we will explain what zero knowledge proofs can do. We’ll also discuss how they work and where they have been deployed. The truth is more detailed and fascinating than what you may think.
Three properties
The proof has to satisfy three properties. If the statement was true, and both provers and verifyors followed the protocol then the verifier would always accept the proof. The statement must be true to convince the verifyor that it is correct. A cheating proofer can only do this with a very small probability. Verifiers have zero-knowledge if they don’t know if the statement is false.
Third property, the most counterintuitive. How do you know if a calculation is correct without knowing anything about it beforehand? Answer lies in structure of proof system. The prover encodes its computation in a polynomial formula, then commits it using cryptographic commitment schemes, before responding to the random questions from the verifier. Verifiers can check responses to the commitment without seeing the actual polynomial.
The random challenges in non-interactive, zero-knowledge, proofs are replaced with a hash-function applied to the committment. It is known as the Fiat Shamir heuristic and allows the prover generate the complete proof without having to communicate back and forward. It is then a short string of information that can be independently verified by any person.
For zk-SNARKs, security relies on the difficulty of computing discrete logarithms on elliptic curves. The security of zk SNARKs relies on how difficult it is to compute discrete logarithms over elliptic contours. In zkSTARKs security is dependent on hash function collision resistance. This assumption is weaker, but more conservative. The proof system will break if either assumption is wrong. The choice between zk-SNARKs and zk-STARKs There are many factors to consider when evaluating the performance of a proof, including its size and speed.
Trusted setup with small proofs
zkSNARK is an acronym for Zero-Knowledge, Succinct and Non-interactive Arguments of Knowledge. A zk-SNARK is distinguished by its succinctness: a proof can be validated in just milliseconds, regardless of the complexity of the computation.
Trusted setup is the price of succinctness. The majority of zk-SNARK constructs begin with a ceremony in which a series of reference strings is generated. Both provers and verifyors use these strings. If they are not destroyed properly, anyone could produce fake proofs. It is also known as toxic waste.
Modern, trusted ceremonies are based on multi-party computing protocols in which hundreds or thousands each participant contributes randomness. As long as one participant destroys the randomness they contributed, there is a security guarantee. Zcash was the first to use this method with its Powers of Tau Ceremony, but subsequent projects refined it.
The newer zk SNARK constructions, like PLONK or its variants, use a universal setup that can be updated. This means the same setup is reusable for multiple circuits. Additional participants can also strengthen the setup with time and without having to start from scratch. It reduces but doesn’t eliminate the concern over trusted setup. Fundamentally, the trade-off is still smaller and faster proofs for an assumption of trust that only occurs once.
Zk-STARKs : No setup trusted, bigger proofs
Zero-Knowledge Transparent Scalable Argument of Knowledge is zkSTARK. Transparent simply means that no trusting setup is needed. Toxic waste is eliminated because the reference strings generated are generated using publicly verified randomness. Scalable is the term used to describe the fact that the proving time increases almost linearly as the computational size grows.
A trade-off comes in the form of proof size. The size of the zk STARK is usually between tens and hundreds of kilobytes versus a few hundred byte for a standard zk SNARK. In a blockchain environment where data storage costs are high, the difference can make a big impact. This is because the verification times for STARKs are also longer. However, they’re still quick enough to be practical.
StarkWare is the main commercial proponent of zk-STARKs. The argument they use is that transparency, coupled with the quantum-resistant properties of using hash functions and not elliptic curved cryptography, make STARKs a better choice in the long run, even if it means requiring larger proofs. Quantum computers may or may not threaten the elliptic curvature cryptography, depending on when they are developed. However, it is argued that a conservative security approach appeals more to applications in which long-term robustness and efficiency matter.
ZK Rollups: The scaling application
ZK rollups is the current most popular practical application for zero-knowledgeproofs on blockchain. The rollup process executes all transactions, off the chain. It then batches the transactions together and generates zero-knowledge verification that they were valid. Main chain then verifies this proof. This is hundreds of times cheaper than performing each transaction one by one.
The architecture allows Ethereum’s layer 2 network to handle thousands of transactions at the price of one proof-of-work on layer 1. ZK rollups such as those built on Ethereum infrastructure Gas costs can be reduced by up to 90% compared with executing transactions on the mainnet.
The ZK rollup project in late development or production as of the mid-2026 includes zkSync Era. Scroll, Polygon zkEVM. Linea and Taiko. Each of the projects uses a different proofing system. They also make different compromises in terms of EVM compatibility. zkSync relies on a PLONK-based PLONK virtual machine. Scroll aims at byte level EVM equivalence with a zk SNARK proofer. Polygon zkEVM combines STARK with SNARK to create a recursive architecture.
In proof generation, the competition among these projects has led to rapid innovations. In the last 2 years, time to prove has dropped from several hours down to a few minutes. Vitalik Buterin introduces the GKR protocol for Ethereum This is another step towards making ZK verification routine rather than being a bottleneck in terms of computational resources.
Applications of privacy beyond the roll-up
Zero-knowledge proofs (ZKPs) were initially developed to provide privacy rather than scalability. Zcash launched in 2016 was the first major Blockchain to use zk SNARKs. The sender, recipient, and transaction amount of a shielded Zcash are hidden. This ensures that the public cannot see the details.
This privacy app extends to financial transactions. Identity attributes can be verified without disclosing the data. Users could verify that they’re over 18, without divulging their date of birth, they can prove to be citizens of a country, without disclosing their passport number or they can prove they have a credential, without divulging the institution who issued it.
ZK-based systems of identity verification have been implemented by projects like Worldcoin ID and Polygon ID. Worldcoin relies on zero-knowledge to prove that an iris scan was performed by a device, without tying the scan back to a specific person. Ethereum ecosystem projects As a primary, ZK is increasingly being used to identify users.
Privacy use cases face regulatory obstacles. Multiple financial regulators around the world have voiced concern about how fully private transactions may facilitate money laundering and terrorist funding. A key policy debate in cryptography is about the tension that exists between transparency and privacy. The zero-knowledge principle sits at the heart of this.
Zero-knowledge Proofs Do Not Cover
Proofs based on zero-knowledge guarantee the integrity of a computation: they ensure that it was done correctly. These proofs don’t guarantee the accuracy of the inputs, whether the computation is worth executing, or if the system around which the proof has been built does not contain bugs.
The ZK can be used to prove all the transactions within a batch are valid in accordance with its rules. The rollup cannot verify that the rules are accurate. The rollup could have a bug that caused the proving or smart contract circuit to produce proofs validating invalid state transitions. Audits and testing of ZK projects revealed and fixed critical bugs.
Data availability is also not eliminated by zero-knowledge proofs. ZK rolls require users to access transactional data in order to reconstruct their state. The rollup operator must be trusted if data is not available.
Computing proofs has a high cost. Verification is inexpensive, but proof generation takes a lot of hardware. ZK provers at large scale usually require servers with hundreds or gigabytes in RAM and special hardware accelerators. The cost of running provers is a major factor in determining who has the money to do so, even though proofs can be checked by anyone.
Checklists for ZK project evaluation
In evaluating projects that claim to be using zero-knowledgeproofs, there are several questions which distinguish genuine implementations from mere marketing.
Inquire first if there has been an independent audit of the system. Soundness flaws can be created when invalid proofs that are not accepted as valid. Be cautious when dealing with a project that is not audited multiple times by independent cryptography firms.
Ask if the system relies on a “trusted setup” and, if it does, what the process was. If the trusted setup is only used by a few participants or is conducted solely by one company, it’s a good indication of trust.
Verify that the contract for proof verification is published by the project and has been confirmed on-chain. The zero-knowledgeproofs might not provide the level of security users are expecting if verification occurs off chain, or using upgradeable contracts that can be controlled by multisig.
Look at the solution for data accessibility. The users will not be able to independently verify the current state of the system if there is no data posted on the blockchain or credible data access layer. The trustlessness of zero-knowledge is no longer possible.
FAQ
In simple words, what is zero-knowledge?
It is possible to demonstrate that you have zero knowledge without actually revealing it. It allows a computer to show another one that a series of transactions are valid, without providing the specifics. The privacy is maintained while allowing for scalability.
What’s the difference between zk SNARKs and zk STARKs
zk-SNARKs are capable of producing very small, usually a few hundred byte proofs. They can verify them quickly but they require a trusted setup once. Zk-STARKs generate larger proofs (typically tens of Kilobytes), but they do not require a trust setup. The two approaches achieve the same objective of verifying computations with zero-knowledge.
ZK rollups can reduce the cost of Ethereum gas.
ZK rollups perform transactions outside the Ethereum mainchain, group them, and create a proof of zero-knowledge that all transactions were valid. The proof is the only thing that gets posted on Ethereum. Verifying one proof costs much less than performing thousands of transactions. This results in gas savings of up to 90%.
Are zero-knowledge proofs quantum resistant?
The proof system is important. Hash functions are used in zkSTARKs, and they’re believed to resist quantum computers. zk SNARKs rely elliptic-curve cryptography that could be theoretically broken by a quantum computer powerful enough. Quantum computers that can break elliptic curvatures are not available yet and will not be for many decades.
Does zero-knowledge make blockchain transactions completely private?
In theory, yes. But in practice there are some tradeoffs. The cost and complexity of creating proofs to support each transaction increases. Unsolicited transactions can also be regulated in countries that demand financial transparency. Zcash offers optional privacy while the majority of ZK rollups are based on scalability, not privacy.
What exactly is a “trusted setup” and why do they matter?
The trusted setup is an one-time event that creates the cryptographic parameters required by some proof systems. The random values that were used in the ceremony could be faked if they aren’t properly destroyed. The modern ceremony uses multi-party calculations where hundreds of people contribute randomness. As long as one person is honest, the setup will be secure.
Which blockchains use zero-knowledge proofs?
Zcash, the world’s first major blockchain with zero-knowledge transactions for private transactions. Ethereum utilizes ZK proofs via layer 2 rollups, including zkSync, Scroll, Polygon ZkEVM, Linea, and Starknet. Mina Protocol utilizes ZK recursive proofs in order to maintain a blockchain of a specific size. ZK is used by several other chains for certain features, such as cross-chain communication or identity verification.
How long does it usually take to produce a proof that you have zero knowledge?
The complexity of computations and hardware being used will determine the time required to generate proofs. On specialized hardware, the proof generation time for ZK rollup batches containing thousands transactions currently takes only seconds or minutes. In two years, proof generation took several hours. Hardware acceleration and improvements in algorithmic performance are driving the trend towards faster proofs, ultimately aiming for real-time generation.
Disclaimer: This is a general informational article and not a legal, financial or investment advisory. Investments in cryptocurrency carry a high level of risk. Before making an investment decision, always do your research. This information is current as of August 1, 2020.
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