Blockchain has become “popular” again. Why has zero-knowledge proof technology become the focus of Silicon Valley blockchain research?


Editor’s note: This article comes from WeChat public account “Silicon Valley Insight” (ID: guigudiyixian), author Juny, 36 氪 released with permission.The concept of blockchain has been around for 10 years since Bitcoin was introduced in January 2009.Even so, what is the blockchain and what can it bring?Many people still see flowers in the fog, seemingly understand.Coupled with the hype of various virtual currencies in recent years, most people pay attention to this complicated new thing.In October, China officially announced that “blockchain is an important breakthrough in independent innovation of core technologies”, making the topic of blockchain in China, which has been silent for a long time, once again become popular at a rocket speed, setting off a new wave of research on technology and applications.As one of the most important underlying technologies of the new blockchain, zero-knowledge proof has also become the focus of current research in academia and industry.In order to explore the cutting-edge development of the latest blockchain technology, Silicon Valley Insight went to the annual San Francisco Blockchain Summit and interviewed one of the speakers of the conference, Benedikt Bünz, the inventor of Bulletproofs theory from Stanford University.Together, they discussed the connotation of zero-knowledge proof technology and its significance to the development of blockchain.Interviewee Benedikt Bünz: Ph.D., Applied Crypto Group, Stanford University, the author of Bulletproofs theory.Chief scientist and co-founder of startup Findora.What is zero-knowledge proof?Benedikt said that the nature of the blockchain is actually cryptography. The concept of the blockchain came into being after the emergence of Bitcoin in 2009.As one of the three basics of modern cryptography, zero-knowledge proof technology was proposed by MIT professors ShafiGoldwasser, Silvio Micali, and cryptographer Charles Rackoff as early as 1985.For their pioneering contributions in modern cryptography and zero-knowledge proofs, in 2012 Shafi Goldwasser and Silvio Micali also won the Turing Award, known as the “Nobel Prize in Computer Science.”Therefore, zero-knowledge proofs existed before the blockchain, and have already reached a very high theoretical level.However, the early zero-knowledge proof theory did not have a good application scenario, only staying at the theoretical level.It wasn’t until the advent of the blockchain that it created opportunities for zero-knowledge proof.(MIT professors Shafi Goldwasser and Silvio Micali won the Turing Award, the picture comes from the network.) In simple terms, zero-knowledge proof means that the prover knows the answer to the question, he needs to prove to the verifier the fact that he knows the answer, butAsk the verifier for no information.Does it sound a little dizzy?Never mind, give you a simple example.You and your companion have a room in front of you, and there is a code lock on the door. You need to prove to your companion that you know the lock code, but you don’t want to tell him what the code is. So what should you do?Your partner knows that there is a book in the room where he wrote his name, and you just need to show it to him to prove that you can enter the room.In the process, you (certifier) ​​don’t need to tell your partner (certifier) ​​the room password directly, but through this book with his name written to prove to him that you know the password.What is the relationship between zero-knowledge proof technology and blockchain?The concept is not difficult to understand, but why is it that zero-knowledge proof is important for the next development of blockchain?Let’s first briefly understand the principle of Bitcoin trading.Suppose A wants to transfer a bitcoin to B. At this time, we consider bitcoin as a check, and A wants to transfer this check that he owns to B. Then he needs to create a new check for B, at the same time in front of B.Tear your original check.In this process, the transaction addresses of the two must be related.So what are the consequences of this?(Silicon Valley Insight Mapping) Benedikt explained to the detective that the anonymity of Bitcoin is only reflected in the fact that the address is not associated with a real person, but all transaction information is completely public.Therefore, once someone knows your Bitcoin address (for example, he transfers it to you for posting), he can check all your transaction history and balance from the chain.And this kind of privacy exposure will lay a deep hidden danger for large-scale commercial applications in the future.For this reason, zero-knowledge proof technology is particularly important.What changes can it make?Take Zcash, which is the first time that zero-knowledge proof technology is applied to digital currency, as an example, it is still A to transfer a ZCash to B.Unlike Bitcoin, A’s certificate will have a series of certificate numbers. When A is transferred to B, A does not need to exchange addresses with B directly. Instead, there is a third-party certificate invalidation list.”Invoice Code”, using the “Remarks Void” method to prove that Alice’s check has expired, and at this time B will get a new valid voucher number.In this way, B does not need to see A’s certificate, but still realizes the transfer of asset ownership.(Silicon Valley Insight Mapping) And in this zero-knowledge proof process, two main issues are involved, one is who is doing this trusted third-party (trusted set-up), and the other is verifying whether performance is good enoughproof size).Therefore, many scholars have begun to study different solutions for these two dimensions, and some have focused on performance issues, such as Snark, Sonic, PLONK, Libra (not Facebook’s libra) proposed by Berkeley, etc.”Trusted third party” issues, such as Bulletproof proposed by Benedikt and Supersonic he is optimizing.Are so many nouns already dizzy?Benedikt joked that, in simple terms, you can think of zero-knowledge proof as an orchard, Bulletproof, Snark, Sonic are like oranges, apples, bananas and so on.(The picture comes from the Internet, the copyright belongs to the original author) Bulletproofs invented by Benedikt, innovatively invented the setting that does not require a “trusted third party”, Monero Monero, JPMorgan, etc. are applications based on Bulletproofs.This technology has reduced Monero’s fees by 97%.The benefit is that using short proofs enables privacy transactions of low to medium complexity.However, the downside is that privacy support for very complex transactions is not ideal.Therefore, when the entire blockchain is proven to be valid, Bulletproofs are limited.Benedikt also emphasized that the current zero-knowledge proof technologies actually have their own emphasis and strengths, and everyone is currently learning from each other and making progress, hoping to find an optimal solution in multiple dimensions.”Like Newton said, if you can see farther, it is because you are standing on the shoulders of giants. All our researchers are climbing this ladder step by step.” In what fields can zero-knowledge proof be applied?Everyone must be wondering, what kind of changes can zero-knowledge proof bring to the industry?Benedikt said that before the advent of the blockchain, zero-knowledge proofs had many applications in the computer field as an encryption technology.For example, the web browsers we often look at use related technologies to ensure security in order to prevent hackers from tracking the address.Another example is some big data analysis companies, in order to protect the privacy of customers, draw data analysis conclusions without directly seeing each data and address.And he believes that after the emergence of the blockchain, with the development of the financial industry, zero-knowledge proof technology will play a huge role in the financial field.At present, Benedikt, as the chief scientist, and his Stanford doctoral students Charles Lu and Ben Fisch have co-founded a project called Findora, with the vision of establishing a global financial decentralized network, protocols, bottom layer and standards, which has now received Stanford fundsThe conference was supported by commercial guidance from former Foundation CEO John Pauls.(Picture from the official website of Findora) The reason for doing this project is that they believe that the current maturity of the zero-knowledge proof technology has reached a stage where it can be commercialized, and the development of the financial industry, especially the development of digital currencies, will be zero.Knowledge proves that there is a strong technical need.Why is there such a demand?First, let’s take a look at the three main payment methods currently on the market.The first is a completely decentralized chain of FacebookLibra, Ethereum, Bitcoin, etc. that can be used for payment.The second is a centralized Alipay, WeChat payment, and bank transfer.The third is the privacy protection ZCash, Monero, Findora and other payment networks.Of these three payment methods, the decentralized Libra, Ethereum, and Bitcoin have high transparency to the public, but the privacy is the worst; the centralized institutions of traditional third-party giants are only known to third parties due to transaction information, which belongs toThe privacy is medium; the untraceable privacy payment using zero-knowledge proof technology has the highest privacy.Obviously, most users will definitely not want their property transaction amounts to be seen or tracked by everyone, thus creating a need for privacy.In addition to monetary payments, in financial applications such as hedge funds, exchanges, and P2P, not only privacy is required, but also complex compliance is required. This requires financial networks to support very complex transactions while, Can also guarantee a high degree of privacy and efficiency, while also ensuring the auditability of transactions, in order to gain considerable trust from customers.This is what the Findora project wants to do. It establishes a financial platform that supports complex transactions and also has high privacy, efficiency and auditability through zero-knowledge proof technology.(The picture is from the Internet, the copyright belongs to the original author) For example, in the management of investment funds, the current funds can see which investors have subscribed for how many shares of the fund, but through zero-knowledge proof technology, the fund can be madeThe manager only knows the overall fund size, but will not know exactly how much money each investor will receive.In addition, they have developed several zero-knowledge proof tools.Some can be used for privacy protection calculations, and have a great role in helping to seal bid auctions, dark pool transactions, fair lottery, etc.There are also tools for demonstrating compliance that financial institutions can use to prove compliance while protecting privacy.Benedikt said that the current Supersonic technology they developed for Findora is the first SNARK that does not need to be trusted, and the size of the proof is very small, for example: a complex 1 million grid, the proof only needs 10-20KB.This further guarantees the computational complexity, credibility and verification speed.(Benedikt did technology sharing at the conference) What other difficulties do blockchains need to break through?In addition to the privacy issues solved by zero-knowledge proofs, Benedikt told the small investigator that he believes that transaction efficiency and energy consumption are two other issues that need to be addressed in the process of blockchain technology improvement.The blockchain has achieved decentralization and security, but the increase in transaction speed has become a problem.Take bitcoin as an example, bitcoin currently supports a maximum of 7, 8 transactions per second, but in traditional payments, visa can support a transaction volume of 3,000 transactions per second.Obviously, if the blockchain is to develop on a large scale, the increase in transaction speed is an obstacle that must be overcome.In addition, the problem of energy consumption needs to be solved urgently.In the 10 years since Bitcoin was launched, as prices continue to break new highs, the total energy consumption of the Bitcoin network has also continued to grow at an alarming rate.According to the latest report released by the Cambridge University research institute, the entire bitcoin network’s 2019 power consumption levels have exceeded Switzerland, Greece and other countries.Benedikt said that without solving the problem of energy consumption, the development of blockchain is not sustainable.(Bitcoin’s energy consumption in 2019, the picture comes from the research of Cambridge University, the copyright belongs to the original author) To address these issues, experts and scholars are now studying in different directions.In addition to Benedikt, I also saw many young scholars like him at the summit. They came from the United States, Europe, China, Japan … Some of them are studying for PhD, some are blockchain technology practitioners, everyone gathered together to shareTheir latest research.As Benedikt told me, researchers around the world are working together to climb the peak of this new thing about blockchain.It is these people who have infinite enthusiasm for the study of cryptography that constantly inject fresh blood into the blockchain and illuminate its path, so that the future development of the blockchain is unknown and fascinating.Want to learn more about the Findora project?Check it out: Want to learn more about Zero Knowledge Proof Technology?You can view the following papers: 1.https: // // // (Thanks to Dr. Yuncong Hu and Zhang Jiaheng from University of California, Berkeley for their theoretical guidance in the writing process).