What Is Zero-Knowledge Proof?

Zeker, hier is de vertaling van de tekst naar het Engels:

A zero-knowledge proof (ZKP) is a cryptographic method that allows one party (the prover) to prove to another party (the verifier) that they know certain information without revealing the information itself (the secret). This concept was first introduced in 1985 by S. Goldwasser, et al. and now forms the basis of blockchain and cryptocurrency systems today, ensuring data security and privacy while establishing trust.   

Key properties:

• Completeness: If the prover’s claim is true, the verifier will always accept the proof.
• Soundness: If the claim is false, the verifier will reject the proof with high certainty.
• Zero-knowledge: The verifier learns nothing beyond the fact that the claim is true, preserving the secrecy of the information.

How does a zero-knowledge proof work? 

ZKP works by creating a mathematical framework where the verifier gains confidence in the prover’s claim without receiving any sensitive data. The prover has some secret knowledge, such as a password, that they want to prove to the verifier. The prover may either interact with the verifier through a series of challenges and responses, or create a proof once that can be independently verified. For example, the prover might be asked to show that they can correctly access something hidden. If the prover does not have the secret knowledge, they will fail to provide the correct response. If they do, the verifier gains confidence in the prover’s claim of knowledge but learns nothing about the secret itself, making ZKPs powerful tools for maintaining privacy in financial transactions and identity verification.

Types of ZKP techniques:

Interactive techniques (IZKP) 

IZKPs require back-and-forth communication between the prover and verifier to confirm knowledge. During the process, the verifier challenges the prover with random questions or tasks to confirm the prover’s knowledge without revealing the secret. A common technique is the Fiat-Shamir Heuristic, where a random value represents a challenge for the prover. The prover uses their secret knowledge to provide a response, which is designed in such a way that, if they know the secret, they will always provide the correct answer. The verifier can check the validity of the response without learning about the secret.

Non-interactive techniques (NIZKP) 

NIZKPs use precomputed proofs that can be verified without direct interaction between the parties. The most common example is the zk-SNARKs (Succinct Non-Interactive Argument of Knowledge) Proof, used in cryptocurrency to enable private transactions. These protocols allow users to prove the validity of transactions by generating a cryptographic proof, which confirms that the transaction adheres to the rules without revealing sensitive details like the sender, receiver, or amount.

Simple ways to explain zero-knowledge proof: 

Here are a few scenarios to explain how ZKP works:

• Imagine you (the prover) know the combination to a locked box and you want to prove to the verifier that you know it without revealing the code itself. You would take a picture of an item from inside the box, which the verifier knows should be there, and send it to the verifier as proof that you have access. (NIZKP)
• Suppose you have a jigsaw puzzle with a hidden picture. You can prove to a friend that you have completed the puzzle by showing them one piece in its correct position while keeping the rest of the image hidden. By repeatedly showing different correct pieces, they will be convinced that you’ve solved the puzzle without ever seeing the entire image. (IZKP)

Reasons for using ZKP:

• Data privacy: To enhance security by allowing authentication and verification without sharing personal or sensitive information.
• Cryptocurrency: To ensure transaction privacy while maintaining network integrity in blockchain technologies.
• Access control: To validate user credentials without exposing passwords or sensitive details, reducing attack risks.
• Regulatory compliance: To meet data protection standards, such as the GDPR, by ensuring user privacy and minimizing data exposure.

Examples of ZKP:

• Password verification: Proves knowledge of a password without revealing it, reducing the risk of interception.
• Blockchain privacy: Ensures private transactions on blockchain networks while preserving overall system integrity, as seen in cryptocurrencies like Bitcoin and Zcash.
• Identity verification: Confirms a user’s identity for secure access without exposing their full personal details, enhancing data protection.

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