Source: Nuclear Finance, the original title "Bitcoin is inevitable"
In the office of Guomao, Ma Zhibo stepped on and walked around, looking excited.
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As a Ph.D. in astrophysics and a former financial derivatives investment expert at Goldman Sachs, he has been watching the movements across the ocean for more than a month.
As early as more than a month ago, a research report by US technology giant Google (Google) briefly appeared on the National Aeronautics and Space Administration (NASA) website, and was quickly removed. On October 23, in the special issue of the 150th Anniversary of Nature, the Quantum supremacy using a programmable superconducting processor was co-authored by 77 authors. It was published, and Google’s “quantum hegemony” was fully displayed.
Cover of the 150th Anniversary Special Edition of Nature
"The impact of this matter is too great." The paper throws the words "Guantum Supremacy", which quickly caused a sensation and won extensive discussion.
In Google's view, this is a landmark event in the quantum field that resembles "Hello World." In an interview with the media, Google CEO Sundar Pichai believes that this achievement is comparable to the Wright brothers' first flight in 1903.
"Official propaganda. The United States has achieved quantum hegemony!" Ivanka Trump, the daughter of the US president and senior adviser, wrote on his Instagram. This can be seen.
Ivanka congratulates Google on achieving "quantum hegemony"
It is reported that in order to achieve this major scientific and technological achievements, Google has been working hard for 13 years.
The approximation of "quantum hegemony", whether Bitcoin is conquered or not is a sword of Damocles hanging over its head.
"In fact, before the advent of Bitcoin, the threat of quantum computing already existed." Li Wansheng, founder of NBSChain, believes that, first of all, the actual threat of quantum computing does not exist yet. Second, "quantum hegemony" is to solve problems in specific areas. "Hegemony" must not be the solution to all problems.
At the same time, many projects such as Ethereum and Quantum Chain are closely watching the research and development of anti-quantum computing ciphers, among which there are many practitioners. In the interview with the Nuclear Finance App, Quantum Chain founder Shuai Chu believes that from the starting point of Google’s “quantum hegemony”, it cannot and does not intend to solve any practical calculation problems. Therefore, I think its practical significance is relatively limited. The practical application of quantum computing is still far away.
After a hot speculation, whether it is prepared or not, it is a puzzle that is both unresolved and painstaking.
In the article "Quantum Hegemony with Programmable Superconducting Processors," Google claims to successfully demonstrate "quantum hegemony." Among them, it uses its experimental quantum computer, which takes about 200 seconds to complete the calculations that the traditional supercomputer can complete in 10,000 years.
It is understood that the quantum computer used by Google has a chip called "Sycamore". From the chip's chip map, Sycamore is purple, engraved with "Google AI Quantum" on one side, and "Sycamore" and a tree-shaped pattern on the other.
The data shows that the processor consists of a two-dimensional array of 54 Transmon qubits. Since one qubit does not work effectively, only 53 qubits are used in this experiment.
However, quantum computers are not Google's first.
As early as the early 1980s, Benioff proposed the idea of quantum computing. He designed an executable, classical analog quantum machine, which is considered to be one of the prototypes of quantum computers.
"The information unit of a traditional computer is a bit, which is operated based on the two states of 'high' and 'low' potential of the digital circuit. These two states are represented by '0' and '1'." Ma Zhibo said, "In a quantum computer. In the basic information unit is a qubit (Qubit), which can exist in a superposition state of two logic states, that is, a corresponding quantum state superposition of '0' and '1'. Compared with a binary conventional computer, the number of operations Significantly reduced, the time required is correspondingly shortened."
He said that quantum computers have powerful quantum information processing capabilities, but the full capabilities of quantum computers are not yet known.
The paper shows that Sycamore's calculations are to prove that a random number generator conforms to the "random" standard. Even the most advanced traditional supercomputer "Summit", it takes 10,000 years to sample 1 million instances of a quantum circuit, and Sycamore only takes 200 seconds to complete the operation.
"Sycamore broke Moore's Law in just 200 seconds to complete the supercomputer's 10,000-year mission." Ma Zhibo said. Moore's Law means that the chip computing power of traditional computers doubles every 18 months. Thus, this doubling of Sycamore seems to have completed an exponential leap.
However, there are different opinions in the industry about Google’s claim to achieve “quantum hegemony”.
As a competitor of Google, IBM did not buy it, and soon poured cold water. They believe that this goal has not been achieved in accordance with the strictest definition of "quantum hegemony."
IBM researchers point out that Google's so-called "the most advanced supercomputer takes about 10,000 years" to complete the task, the ideal simulation on a traditional computer system, only 2.5 days, and the fidelity is much higher. This is actually a conservative, worst-case estimate. In addition, Google did not fully consider "a lot of disk storage" when comparing.
Zhang Fuchun, director of the Center for Excellence in Topology in Topological Quantum Computation of the Chinese Academy of Sciences, had previously said in an interview with Xinhua News Agency that such demonstrations are like "Alpha Go" in the field of artificial intelligence, which can defeat the most powerful Go players of humanity, but not It is versatile. At the same time, there is a view that whoever takes the lead in developing a quantum computer will have a "nuclear weapon."
From a technical perspective, there are not many teams with research capabilities. Therefore, Google’s claim that the name “quantum hegemony” is true is not a recognized conclusion.
Safe and worry-free now
In the field of cryptography, it has always been a battle between the encryption party and the decryption party.
“The blockchain puts many advanced cryptography theories into the application.” Because of this, in the eyes of the currency circle, Bitcoin is the first application scenario of blockchain technology.
When the "quantum hegemony" came out, a stone provoked a thousand waves. Some people think that quantum computers and blockchains are natural "spears and shields."
Ma Zhibo said that quantum computing may impact Bitcoin's proof of work (PoW) and payment process.
He further pointed out that there are two encryption algorithms for Bitcoin, namely asymmetric encryption algorithm for digital signature (Elliptic Curve Encryption Algorithm ECDSA) and SHA-256 as a hash function. The former is mainly used to generate public and private keys, and the latter is mainly used to generate the wallet address from the public key and the PoW of the mining process.
"In theory, theoretically, quantum computers can use the Shor algorithm to solve the ECDSA and use the Grover algorithm to crack the SHA-256." Ma Zhibo believes that this theoretical possibility really occurs in practice. Still to be proved.
The first research found that only the earlier version of the P2PK type address will directly expose the public key, about 1.77 million bitcoin exists under this address; in addition, if the same address is used repeatedly to send and receive bitcoin, it is also possible to expose the public key. This part of the bitcoin is about 5 million; all the remaining bitcoins are stored in the address where the public key is not exposed.
"For those addresses that have already exposed the public key, the user only needs to transfer the currency to an address that is not exposed to the public key to completely avoid the possibility of being cracked," he said.
What is even more disturbing is that although quantum computing will theoretically affect public key cryptosystems and even affect the security of blockchain systems such as Bitcoin, this threat seems to be far away from us. Shuai Chuan said that studies have shown that bitcoin may be broken within 7 days when it reaches 1.7 million qubits. According to foreign media reports, a quantum computer with more than 4,000 qubits can break up the blockchain. But we know that Google’s announcement this time is only 54 qubits. Moreover, as the number of quantum bits increases, technology and cost are still to be solved.
In other words, to achieve the theoretical number of qubits that can break through the Bitcoin network, it is long and long.
At the same time, Peter Todd, a former developer of Bitcoin Core, also wrote that Google's quantum breakthrough is aimed at the primitive type of quantum computing, which is far from breaking the level of cryptography. We don't even know if it is possible to extend quantum computers, and adding quantum bits is likely to lead to double the cost increase.
Previously, Whiting Diffie, known as the father of modern cryptography, also said at the Boao Forum for Asia that quantum computing would only threaten a very narrow but very important area of cryptography, which led to the establishment in the 1970s. The public key cryptosystem has become vulnerable. But many of the techniques in cryptography, including the hash coding used by blockchains, are not vulnerable to quantum computers.
Aside from the quantum "threat" theory, although we can not eliminate the quantum computing effect paradox, it can promote its positive effects.
The currency is easy to see. The technical team said that if we look at the development of human science and technology from a dialectical perspective, just as the influence of relativity and quantum theory on traditional mechanics, higher computing technology will certainly challenge existing algorithms and techniques, which is in the history of cryptography. It is not uncommon, as happened in history, there will be new technologies and solutions to meet the needs of the encryption field.
It should also be pointed out that the consensus algorithm in the blockchain technology system has shown the development trend of a hundred flowers after PoW, and there are dozens of them.
Some of these consensus algorithms are still loyal fans of quantum computing. The quantum theorist at the University of Texas at Austin, Scott Aaronson, once said that quantum computing can reduce the suspicions of PoS skeptics because "quantum hegemony" experiments can produce provable random numbers.
The trend is forced to "tradition"
"The wave of the times is always one wave after another, and the quantum computer era is bound to come," Ma Zhibo said.
According to industry experts, in the next 30-50 years, quantum computers may break the SHA-256 algorithm currently used by Bitcoin. But he stressed that before that, quantum computing is likely to impact Bitcoin's proof of work (PoW) earlier and affect the payment process of the entire network.
The implication is that quantum computers and Bitcoin will have a battle sooner or later. As Chen Bowei, the initiator of password punk Taiwan, said that distance is not equal to impossible.
In the view of the "threat theory" supporters, if at some point, someone is the first to gain the quantum computing power to break the SHA-256 algorithm, it will bring a devastating blow to Bitcoin.
As we all know, in the Bitcoin global network, the mining machine uses the computing power of the chip, continuously performs hash operations, finds random numbers that meet specific requirements, and wins the billing rights on the public account book, thereby obtaining the system-rewarded bitcoin. .
"Assume that someone really has this 'God' perspective at a point in time, and quickly 'capturing' wealth becomes a simple comparison of input and output to quantum computing. Further, once the 'quantum hegemony' side With more than 51% of the computing power of the entire network, block billing will have problems. Compared with the rest of the miners, they will get most of the new bitcoin rewards with “cabbage price”. The confidence and value of the bitcoin network will be Will be greatly hit," Ma Zhibo said.
It sounds like a bridge between "the gods fight, the mortals suffer."
"From a philosophical point of view, the future development of science and technology, there are spears in the world." Li Wansheng believes that Google's news of quantum computing advantages may be a good thing for the blockchain. From the current point of view, quantum computers are far from landing, but as long as there is such a possibility, we must take it seriously.
He said that there are encryption algorithms to crack the encryption algorithm, and then there will be more suitable encryption algorithms, the world is always progressing and developing in the contradictory process of contradiction.
The best way to deal with the threat of quantum computing is to prepare for the development of anti-quantum technology. According to the Nuclear Finance APP, many cryptography big coffees have been put into action for anti-quantum computing.
In September this year, in the "White Paper on the Development of Quantum Computation (2019)" compiled by the CCID Institute of Electronic Information, it was stated that there are five main types of defense against possible quantum computing attacks, namely code-based passwords. Hash function based password, multivariate password, lattice password and homologous password.
"Encrypted digital currency can be upgraded to the corresponding algorithm before the arrival of quantum computing threats, thus completely avoiding security issues." Shuai Chu believes that the grid-based anti-quantum password has been widely circulated in the circle.
There is also media dug out. In 2010, Nakamoto gave an answer to the question of how to deal with the threat of quantum computing. At that time, Bitcointalk user "llama" about the quantum computer, Nakamoto returned, "It is true that if it is suddenly cracked, the signature will be destroyed; but if it changes slowly, the system still has time to switch to a stronger function, and Re-sign all your assets."
In Ma Zhibo's view, when catastrophic cracking occurs, Bitcoin can solve problems at any time with forks.
"Currently, Bitcoin uses the SHA-256 algorithm, which can be upgraded to SHA-512, 1024, 2048… There are data displays that can even be upgraded to millions." He believes that this is the most conventional defense against quantum computing. Ideas. In addition, it should be pointed out that when it is increased to a certain length, although it can still grow, the storage becomes very troublesome. At this time, all kinds of common computer encryption may not be safe, and using quantum encryption to defend quantum attacks is the only way out.
"This is probably a 'magic height one foot, a high one foot.'" Ma Zhibo thoughtfully told the Nuclear Finance APP.
In the past few days, anxiety and thinking triggered by a paper have continued. He visually calls the game relationship between quantum computing and bitcoin "Uncharted Waters". "The water level has never risen so high. It is still a mystery where it will be drowned." Ma Zhibo said.