Zero-Knowledge proofs in a nutshell:
- Zero-knowledge proofs allow one party to prove they know something without sharing the data itself.
- In blockchain, ZKPs enhance privacy, security, and scalability by validating transactions without revealing sensitive information.
- Starknet uses ZK proofs—or, more accurately in its case, validity proofs—to scale blockchain. As a Layer 2, Starknet executes transactions in bulk and uses proofs to enable the Layer 1 (currently Ethereum, soon Bitcoin) to verify the transactions with minimal computational effort. The goal in this case isn’t to maintain privacy, but to enable the Layer 1 blockchain to accept the transactions without having to execute them itself.
What are zero-knowledge proofs in blockchain?
Zero-knowledge proofs (ZKPs) are cryptographic methods that let one party (the prover) prove a statement’s validity to another (the verifier) without revealing any additional information. In blockchain, ZKPs are used to verify transactions without exposing details like account balances or recipient addresses. This approach ensures privacy and security while maintaining the network’s integrity.
In a Layer 2 (L2) network like Starknet, the prover might be a user or a smart contract demonstrating ownership of a balance or transaction. The verifier, which could be another smart contract or network node, verifies the proof through various techniques. These methods help reduce congestion on the main Ethereum blockchain, speed up transactions, and maintain high data security standards.
What are zero-knowledge proofs not?
ZKPs are often confused with validity proofs, but they serve different purposes. While ZKPs are designed to prove that a statement is true without revealing the underlying data, validity proofs focus on efficiently verifying the correctness of computations without necessarily preserving privacy. In blockchain scaling solutions like Starknet, the term “zero-knowledge” is commonly used; these validity proofs ensure transaction integrity with minimal computational effort, emphasizing accuracy and efficiency over data confidentiality.
Zero-knowledge proof benefits
ZKPs are an important element in the blockchain space because of the distinct benefits they offer:
- They enhance privacy, allowing users to validate critical information, such as account balances, without exposing sensitive details.
- Transactions validated through ZKPs are highly secure, minimizing risks of fraud and manipulation in the network.
- ZKPs improve scalability by verifying batches of transactions offchain, reducing the computational load on the main blockchain and significantly lowering costs.
- They support regulatory compliance by enabling organizations to prove adherence to rules without disclosing proprietary or personal data.
How do zero-knowledge proofs work?
ZKPs operate through an interactive process between two participants: the prover and the verifier. The prover seeks to prove a statement’s validity, such as: “I have sufficient funds for this transaction” without revealing any sensitive underlying information. The verifier confirms the proof without learning anything beyond the truth of the statement.
The process begins with the prover presenting evidence, known as the witness, that supports their claim, including demonstrated ownership of an account balance or access rights to a resource. The verifier then issues a challenge, using cryptographic algorithms to validate the claim against specific criteria:
- Completeness: If the prover’s claim is valid, the verifier can confirm it.
- Soundness: If the claim is false, the verifier cannot be tricked into accepting it.
- Zero-knowledge: The verifier learns only that the claim is true, without accessing additional details.
Once the prover responds to the challenge with the appropriate proof, the verifier evaluates the response. If the proof satisfies all conditions, the verifier confirms its validity without ever gaining access to the sensitive data behind the statement. The completed proof is then submitted onchain, where it undergoes final verification.
Zero-knowledge proof use cases
Some of the most impactful applications of ZKPs include:
- Private transactions
- Blockchain scaling
- Identity verification
- Healthcare data sharing
- Decentralized voting