# Will Blockchain Survive in Post-Quantum World? – A MANX View

Every day millions of cyber attacks are identified around the world, with more millions likely undetected. Hackers use a wide array of tools such as malware, distributed denial of service attacks, Spam and phishing to wreak havoc and/or enrich themselves. At the same time, the number of financial transactions that leverage blockchain technology and cryptocurrencies is growing rapidly, making blockchain a valuable and attractive target for hackers. As Willie Sutton said when asked about why he robbed banks, “because that’s where the money is.” Increasingly, the money is stored in blockchain.

Blockchain is protected by cryptography-based security. From the Caesar cipher to Enigma and modern encryption methods, cryptography has been enhanced and reinvented throughout its history. In the modern era, enhancements are needed to maintain security in the face of advances in code-breaking theory supported by huge increases in computing power. “Computing capability and encryption capability are locked in an information age arms race”, said Dr. Yawei Cui, the co-founder of MacroChain and the MANX project.

The nuclear bomb of this cryptography arms race is quantum computing, a developing technology that will potentially shake the very foundation of the perceived most secure network. “Bitcoin will be worthless if RSA256 can be back-engineered by quantum computing, maybe in 20 years”, predicted a MANX engineer.

How will this computer revolution impact today’s encryption methods, and can popular public chains such as Bitcoin and Ethereum survive in a post quantum world? Dr. Yawei Cui visited MIT professor and MANX advisor, Dr. Vladan Vuletić to find answers. This is their conversation, edited for clarity.

Dr. Yawei Cui:When will we see practical, commercial use of quantum computing?

Dr. Vladan Vuletić : I believe that quantum computers will be with us, so is quantum computing. Maybe they will not be as broad as classical computers, but I think they will be better at certain problems than classical computers.

There is a whole area of quantum communication, which is the idea that you can make communication secure not by some encryption method, but by the fact that you use quantum systems that use individual particles of light for sending the information.

Dr. Yawei Cui:What impact will quantum computing will have on existing public key cryptography systems and internet security?

There are some possibilities, but maybe also some reasons for skepticism. If a quantum computer existed that was sufficiently large, meaning thousands of quantum bits, and that’s at the moment out of range for the next few years. At the moment we are talking about maybe 40, 50, a few hundreds qubits. But if such a large enough quantum computer existed with so called error correction, which is easily to correct some errors that happen during the computation, then it would make our current or at least one of our current encryption methods unsafe and it would have to be replaced by some other mathematical problem. But at the moment that’s not on the horizon.

Dr. Yawei Cui:How strong is the parallel ability of quantum computing?

Dr. Vladan Vuletić : In some sense what all quantum computing is really about is the ability to be parallel, to do parallel computing. What distinguishes the quantum world from the classical world is that simultaneously many different possibilities can be realized all at once.

Just to give you an example from computer logic. In computers, bit is either 0 or 1, but in quantum world, it can be simultaneously 0 and 1 at the same time. Similarly, if you have a complicated computation, one way to think about quantum computing is to say that the quantum computer can explore all these possibilities at the same time, and that’s where people think the power of quantum computing comes from, ultimately this massive parallelism.

One of the challenges is that even though the system can do all the computations at the same time, we can read out only one answer at a time, and so that’s one of the challenges of quantum algorithms. You know, how do we develop quantum algorithms that use this massive parallelism where in the end you can only ask one question to get the answer.

Dr. Yawei Cui:How do you evaluate the impact of the Shor’s quantum algorithm and the Grover’s quantum algorithm on computational science?

Dr. Vladan Vuletić: Let me explain briefly what Shor’s algorithm is.

Today’s encryption RSA basically relies on the fact that if I give you a very very large number, it’s very hard for you computationally on a classical computer to break it up into factors that are prime numbers. Prime numbers are the numbers that we can’t divide any further, so 2, 3, 5, 7… But in principle any number, no matter how big it is, can be broken into a product the multiplication of these prime numbers, but that’s computationally very very intensive.

So on classical computers, the hypothesis says, not for surely known, that all algorithms scale very badly with the size of that number that we call exponentially. So if you just make the number big enough, there’s no known classical computer that can solve this problem.

Now what Peter Shor, a mathematician here at MIT, found out more than a decade ago is that if you had a quantum computer, you could do this calculation efficiently, which means if you had a quantum computer, our current way of encryption, this prime factoring encryption would no longer be safe or secure.

The other thing that you brought up is Grover search. This is really the question of searching large databases. This is when you have a very large database, and you’re looking for some element of some specific characteristics. What’s the fastest way to find it. Grover found out that for a certain type of search, again if you had a quantum computer, it could win over a classical computer.

What is the impact of Shor’s algorithm and also Grover’s algorithm? We need very high performance quantum computers which are out of reach for the next 5 or 10 years. But you need very very large machines, so I think the practical impact in the near future will not be that large. If the quantum computer really existed, it would mean that we would have to find a different encryption, because this known problem would be solvable on a big quantum computer. But as I said, for the next 5 years or so they are certainly out of reach of any machine that we know.

Dr. Yawei Cui:What are your thoughts on the design of post-quantum cryptography? How should humans ensure the security of infrastructure in the post-quantum era such as blockchain, Internet, and cloud platforms?

Vladan Vuletić : This field is called quantum communication. The idea is that you send the information in quantum particles. Basically if these are stolen or get hacked, you know it, because they are the smallest things you can have, the smallest bits of information. Where in classical signal, if I have a cable running from you to me, when you send me some information, the third person can take a little bit of the signal off the cable, and we can never know.

So there is one dream that maybe we can instead send these quantum signals along these cables, then they are protected by quantum mechanics. However, even then, there will always be loopholes because even fully quantum methods are susceptible to some ‘man in the middle’ attacks. Somebody who sits between us, who takes your signal and reads and sends it along to me. I think this is going to be ongoing efforts. But certainly decentralization of information is certainly one way.

A dream brought MANX and Dr. Vladan Vuletić together, along with Nobel Laureate, Harvard University Professor Dr. Eric Maskin, and Dr. Randall Davis, Professor at MIT’s Computer Science and Artificial Intelligence Lab. While other public chain projects claim scalability, interoperability and flexibility, MANX is one of the very few that prioritize long term security, the very foundation of any network. Its proprietary post-quantum encryption method will safeguard information on its platform for decades to come. That is what sets MANX apart.

“I would like you to keep in mind the motivation that brought you (MANX) to this, which is to make it available to a larger society, to a larger group. So from my point of view, if you keep that vision in mind, …it seems to me that what distinguishes your company from others are the efforts that I’ve seen in this.” — —MIT Professor, Dr. Vladan Vuletić

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