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Zero-knowledge proofs for blockchain applications

By Colin McNamara
Published in Technology
September 30, 2022
3 min read

Zero-knowledge proofs for blockchain applications

Cryptographically speaking, zero-knowledge proofs (ZKP) are a way to prove that you know something without revealing what that something is. In the context of blockchain, ZKP can be used to prove attestations of applications and businesses connected to the blockchain. Implementations of ZKP on blockchain networks such as Ethereum, Polygon, Solana, and more can help improve the security and scalability of blockchain applications. Let’s take a closer look at how ZKP works and why it’s so important for blockchain.

How ZKP Works

Generally, a zero-knowledge proof has three parts: a statement, a witness, and a verifier. The statement describes what is being proved, the witness describes the information that can prove it, and the verifier is the party to whom you are proving it. A ZKP witness must be encrypted so that it cannot be tampered with or seen by the verifier to be cryptographically verified.

The protocol for ZKP typically goes like this:

  1. The prover sends the verifier an encrypted statement

  2. The verifier responds with a challenge

  3. The prover responds with an encrypted answer to the challenge

  4. The verifier decrypts the answer and checks whether it matches the challenge

  5. If it does, then the verifier accepts the proof

If even one step in this process is not completed correctly, then the proof is invalidated.

ZKP can allow you to prove something without revealing anything about what you’re proving. This is particularly important in security-sensitive situations where confidential information is needed. To open an account with a bank, you don’t want to disclose your Social Security number or date of birth since these could be used by anyone to impersonate you if you’re trying to prove your identity. ZKP instead lets you establish your identity without disclosing any sensitive information.

Why ZKP Matters for Blockchain

One of the challenges with blockchain is that it can be difficult to scale while maintaining security. That’s where ZKP comes in. Using ZKP, businesses and developers can create more secure and scalable attestations than traditional methods. For example, let’s say you want to attest that a user’s age is over 21 without revealing their age. Using ZKP, you could encrypt the user’s age so that only the user knows what it is and then create a proof that attests to the fact that their age is over 21 without revealing their actual age. This would be more secure than simply asking for their date of birth since that could be easily faked by someone under 21.

Zero Knowledge Proofs in blockchain platforms

Zero-knowledge proofs (ZKP) have emerged as a popular tool in the blockchain space thanks to their ability to allow for private and secure transactions. Let’s explore three implementations of zero-knowledge proofs on three different blockchain platforms: Ethereum, Polygon, and Chainlink.

Ethereum

Ethereum was one of the first blockchain platforms to adopt zero-knowledge proof technology. ZK-SNARKs (the algorithm behind Ethereum’s zero-knowledge proofs) were first introduced on the Ethereum network in 2017. Ethereum’s use of zero-knowledge proofs has allowed it to become one of the most popular blockchain platforms worldwide, with a wide range of applications.

Polygon

Polygon is another popular blockchain platform that makes use of zero-knowledge proofs. Unlike Ethereum, which uses ZK-SNARKs, Polygon uses ZK-STARKs. The advantage of using ZK-STARKs is that they are more scalable than ZK-SNARKs; however, they are also more complex and require more computing power.

Chainlink is a decentralized oracle network that allows blockchains to access data from off-chain sources. This is important because it allows smart contracts to interact with real-world data (such as weather data, stock prices, etc.). One of the ways that Chainlink achieves this is by using zero-knowledge proofs; specifically, Chainlink uses zkRollup technology. zkRollup is a variant of rollup (an Ethereum scaling solution) that uses zero-knowledge proofs to keep data private.

Key takeaways

Due to their ability to allow for private and secure transactions, zero-knowledge proofs (ZKP) are an essential tool in the blockchain space. We have examined three implementations of zero-knowledge proofs on three blockchain platforms: Ethereum, Polygon, and Chainlink. Although each implementation has its advantages and disadvantages, all three illustrate the potential of zero-knowledge proof in blockchain technology.

Learn More:

Zero-knowledge proofs | ethereum.org - An non-technical introduction to zero-knowledge proofs for beginners. (ethereum.org)

Zero Knowledge Proof: how to maintain privacy in a data-based world | BBVA - This technology employs cryptographic algorithms so that various parties can verify the veracity of an item of information without sharing the data itself. (bbva.com)

What Is a Zero-Knowledge Proof (ZKP)? - Zero-Knowledge Proofs (ZKPs) allow one party to cryptographically prove to another that they possess knowledge about a piece of information without revealing the actual data. (blog.chain.link)

Zero-knowledge proofs Archives (a16z.com)

Cryptography - Zero-Knowledge Proofs (crypto.stanford.edu)


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Colin McNamara

Colin McNamara

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