An introduction to ZKP

Zero-knowledge proofs (ZKPs) are a cryptographic method that allows someone to prove insights upon a set of certain information, without ever revealing what that underlying information is. ZKPs can protect any type of information that is typically stored in a database, including passwords, financial data (e.g. bank account balances), personally identifiable information (e.g. social security number), and more. As ZKPs become more widely adopted due to their advantages in privacy, security, and scalability, we believe it is inevitable that consumers will take back control over their personal data and what is shared with third parties.

Evolution of ZKP Technology

The concept of a zero-knowledge proof was first introduced by Shafi Goldwasser, Silvio Micali, and Charles Rackoff in their 1989 paper, The Knowledge Complexity of Interactive Proof-Systems.

The first practical construction of a zero-knowledge proof was the interactive zero-knowledge proof (iZKP), which was introduced by Oded Goldreich, Silvio Micali, and Avi Wigderson in 1991. iZKPs are a form of zero-knowledge proof where the prover and verifier engage in a back-and-forth interaction. During this interaction, the prover sends messages to the verifier, and the verifier sends messages back to the prover, until the verifier is satisfied that the prover knows the information they claim to know.

In the years following the introduction of iZKPs, several improvements were made that lead to the creation of non-interactive zero-knowledge proofs (niZKPs). niZKPs are a form of zero-knowledge proof where the prover sends a single message, or "proof," to the verifier, and the verifier can verify the proof without any further interaction with the prover.

The main advantage of iZKPs is that they are relatively simple to implement and understand. The main advantage of niZKPs is that they are more efficient and can be used in situations where the prover and verifier cannot interact. niZKPs are considered more private as they don't require any interaction with the prover.

SNARKs vs. STARKs

In practice today, there are two main types of niZKPs that are widely used: zk-SNARKs and zk-STARKs:

• ZK-SNARKs (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) are a type of zero-knowledge proof that allows one party (the prover) to prove to another party (the verifier) that a statement is true, without revealing any information about the statement itself. ZK-SNARKs are used in a variety of applications such as privacy-preserving cryptocurrency transactions and identity verification.

  
  

• ZK-STARKs (Zero-Knowledge Scalable Transparent Argument of Knowledge) are a newer type of zero-knowledge proof that offers several improvements over ZK-SNARKs. Like ZK-SNARKs, ZK-STARKs allow one party to prove the truth of a statement to another party without revealing any information about the statement. However, ZK-STARKs are more transparent and do not require a trusted setup, making them more secure and resistant to potential malicious actors.

Benefits of ZKPs

ZKPs are a powerful tool for protecting sensitive information and building secure and private systems. Traditional data protection methods rely on obscuring or encrypting data to keep it secure. ZKPs offer several advantages over traditional methods, such as improved privacy and security, increased scalability and efficiency, and the ability to prove compliance with regulations without revealing sensitive information. ZKPs can be used to create decentralized systems that are more resistant to censorship and tampering. Benefits of ZKPs include:

• Privacy: ZKPs allow one party to prove the truth of a statement to another party without revealing any information about the statement itself. This makes them useful for a wide range of privacy-sensitive applications, such as cryptocurrency transactions and identity verification (e.g. KYC).

  
  

• Security: ZKPs are designed to be highly secure, with many types of ZKPs offering resistance to malicious actors. For example, ZK-STARKs are transparent and do not require a trusted setup, making them more resistant to potential malicious actors and, as a result, provide better protection of consumer data vs. standard practices today.

  
  

• Scalability: Some types of ZKPs, such as ZK-Rollup, can be used to scale blockchain networks by allowing a large number of transactions to be bundled together and processed in a single, compact proof. This is far more efficient (and consequently scalable) than verifying each transaction individually.

  
  

• Verifiability: ZKPs provide a way for one party to prove to another party that a statement is true, without revealing any information about the statement itself. This can be useful in situations where verifiability is important, such as in voting systems.

  
  

• Interoperability: ZKPs have the potential to enable interoperability between different blockchain networks, as they can be used to prove that information on one blockchain is equivalent to information on another blockchain without revealing the underlying data.

  
  

• Compliance: ZKPs can be used to comply with regulations that require data to be kept private, such as HIPAA and GDPR.

  
  

• Multi-party computation: ZKPs can be used to perform calculations and share the results with multiple parties while keeping the input data private.

Real-World Examples of ZKPs

As consumers become more aware of the value of their personal data and the potential risks of sharing it, they are likely to adopt technologies like ZKPs that give them more control over how their data is used. Moreover, as businesses and organizations seek to protect their customers' privacy and comply with data protection regulations, the use of ZKPs may become more widespread. Examples of real-world applications of ZKPs include:

• Identity verification: ZKPs can be used to verify someone's identity without revealing their personal information. Microsoft's ION, a decentralized identity network, uses ZKPs to verify identities without revealing personal information.

  
  

• Financial transactions: Banks and other financial institutions can use ZKPs to enable secure transactions without revealing sensitive information such as account balances. Zcash and Monero are cryptocurrencies that use ZKPs to enable private transactions.

  
  

• Digital Signatures: ZKPs can ensure authenticity of documents without revealing the content of the documents.

  
  

• Access Control: ZKPs can be used to confirm the access of a user to a particular resource without revealing the identity of the user.

  
  

• Cloud security: ZKPs can be used to enable secure multi-party computations in the cloud, where data is processed without revealing the underlying information to the cloud provider.

  
  

• Privacy-enhancing technologies in blockchain systems: Zero-knowledge proofs are used in blockchain systems such as Zcash and Monero to enable anonymous transactions, where the sender, receiver, and transaction amount are kept private.

The Rabbit-hole: Recommend Readings

• Zero-Knowledge Proofs by Ethereum: an overview of zero-knowledge proofs, their history, and their application in Ethereum. It covers the basics of zk-SNARKs, the specific type of zero-knowledge proof used in Ethereum, including their construction and uses in privacy-preserving transactions.

  
  

• Zero-Knowledge Proofs: An Illustrated Primer by Cryptography Engineering: a visual and easy-to-understand introduction to zero-knowledge proofs, with examples and illustrations that help to explain the concepts involved. The article covers the basics of zero-knowledge proofs, including the three properties that define them and the most common types of zero-knowledge proofs.

  
  

• Zero-Knowledge Canon by a16zcrypto: a comprehensive introduction to zero-knowledge proofs, including their properties, use cases, and the technology behind them. It covers the basics of zero-knowledge proof, including their construction and uses in privacy-preserving transactions and other blockchain applications. It also provides an overview of the history and current state of the field.

  
  

• ZK-Snarks: An Introduction by Vitalik Buterin: an overview of zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARKs), a type of zero-knowledge proof, and their applications in blockchain technology. The article covers the basics of zk-SNARKs, including their construction and uses in privacy-preserving cryptocurrency transactions.

  
  

• Zero-Knowledge Proofs: STARKS vs SNARKS by ConsenSys: an overview of the two main types of zero-knowledge proofs: Succinct Transparent ARgument of Knowledge (STARKs) and Succinct Non-interactive ARgument of Knowledge (SNARKs). The article covers the basics of each type of zero-knowledge proof, including their construction and their relative strengths and weaknesses. It also provides an overview of their applications in the blockchain and cryptocurrency space.

  
  

• Decentralized Speed: Advances in Zero Knowledge Proofs by a16z: an overview of how zero-knowledge proofs can be used to achieve hardware decentralization and innovation in the field of privacy-preserving computation. It covers the basics of zero-knowledge proof technology and its potential applications in various industries.