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It's been a long-running worry that quantum computers could one day take down Bitcoin and other crypto mining networks. How likely is that?
Quantum computers are very special machines that can do some calculations a lot faster than normal computers, which are called "classical computers." They are the next step in computer technology.
In recent years, there have been more and more fears that these powerful computers could one day be used to do crypto mining calculations, which are needed to make new blocks.
In theory, people who have quantum computers could, in theory, have a big advantage over everyone else who mines on a proof-of-work blockchain like Bitcoin or Litecoin. This could put the decentralization and security of these types of blockchains at risk. Not only that, but he also got most of the remaining block rewards.
What is quantum computing ?
Classical computers like the one at home or the one you use at work show all bits of data as either a 0 or a 1. To understand how quantum computers work, you first need to know that they show all bits of data as either a 0 or a 1. This type of code is called binary and it is very simple.
Stringing together 0s and 1s makes it possible to run more complex calculations and store more complex data. This is called "bit stringing." But even if you put 0s and 1s together, classical computers still have limited processing power. They can only run one computation at a time and can't do more than that.
quantum computers, on the other hand, can run multiple calculations at the same time because they use quantum bits, also known as "qubits," to do so. When you use qubits, you can show data in three different ways: either a 0 or 1 or both. If you put two things together, it's called a "superposition."
🔮🔮🔮On the Bloch sphere, the state of a qubit is represented by a vector pointing to its surface and the poles correspond to the states |0> and |1>. The more this vector leans toward one pole, the larger its contribution in the qubit superposition.#QuTechAcademy pic.twitter.com/7rSmNGu3vA— QuTech (@QuTech_news) August 18, 2021
What threats do quantum computers pose to crypto mining?
A recently published academic paper in AVS Quantum Science entitled “The impact of hardware specifications on reaching quantum advantage in the fault tolerant regime” outlined two key threats posed by quantum computing to crypto mining, specifically bitcoin (BTC) mining, and the wider ecosystem.
Threat to the proof-of-work consensus mechanism.
Threat to the elliptic curve encryption of digital signatures.
The threat of quantum computers to proof-of-work blockchains
The proof-of-work consensus mechanism refers to the way some blockchains choose honest people to propose new blocks of transaction data to be added to the blockchain. Because there is no single person in charge of a blockchain, it must rely on an automated system that is built into the protocol to keep dishonest people from trying to change the blockchain by making invalid transactions.
Quantum computers have the capacity to perform higher calculations than other types of specialized machines, and so the obvious concern is they could dominate the mining-based competition. According to the paper's authors, however, that threat is thought to be very low because quantum computers have a much slower clock cycle time than application-specific integrated circuit (ASIC) miners do.
In the paper, it says that "the algorithmic speed-up isn't going to be enough to make up for the much slower clock cycle times compared to state of the art classical computing for the near future."
But how can quantum computers have slower clock cycle times but do more calculations than traditional computers, even though they take longer? In the words of Macauley Coggins, the founder of Quantum Computing UK: "The power of quantum computing isn't that it is faster, but that it can make use of quantum parallelism." That's where every single combination of a problem can be worked on at the same time.
In fact, computer scientists in another academic paper entitled “Vulnerability of blockchain technologies to quantum attacks,” which was published in ScienceDirect, suggested it may take as long as to the year 2028 before quantum computers are sophisticated enough to outcompete current ASIC chip technology and perform a majority attack on a blockchain network. That’s not taking into consideration any future improvements to ASIC chip technology by that time.
“Our own calculations based on current ASIC technology, as well as that of other authors, put the earliest likely date that this type of attack will be possible at 2028. However, advances in ASIC technology are likely to push back this date much farther,” according to the study in ScienceDirect.
Cracking public-private key cryptography using quantum computers
People use ECDSA to make mathematically linked public-private keys, which are the digital tools needed to send and receive cryptocurrency as well as show who owns the assets in a crypto wallet. ECDSA is a type of cryptographic system.
A person could figure out someone's private key if they could break this kind of encryption. The person would be able to get that person's public key, which is sent out to the whole network every time a wallet makes a transaction. Accessing a private key is like finding a person's password. It would give the attacker full control over any money that was in the wallet address that the private key came from.
If the same public/private key pair is used to hold the users' bitcoin after the public key is known, then all of the users' bitcoin will be at risk. In the paper in AVS Quantum Science, however, it must be kept in mind that bitcoin wallets don't usually use the same key pairs over and over again."
In order to break the algorithm, how many qubits would it take? According to the paper, a lot:
“... It would require 317 × 106 physical qubits to break the encryption within one hour with a code cycle time of 1 μs. To break it within 10 min with the same code cycle time, it would require 1.9 × 109 physical qubits, whereas to break it within 1 day, it would require only 13 × 106 physical qubits.”
Main problems facing quantum computing technology
While quantum computers are already a thing, the technology is still very much in its infancy.
IBM's quantum processor, dubbed “Eagle,” is considered the world’s most powerful quantum computing system to date – containing 127 qubits. A long way off from the estimated 1.9 billion qubits required to break ECDSA within 10 minutes.
Adding more qubits isn't as simple as it sounds. It all comes down to "quantum noise," which is a huge problem. All kinds of small changes in the environment can make a qubit work less well. "Decoherence" can happen even when there are very small changes in temperature or electromagnetic waves. This means that qubits can't even make a single calculation. The more qubits there are, the more difficult it is to solve the problem.
It's because quantum computers are so sensitive to outside factors that they won't be able to progress very far until this problem is solved. This means that quantum computers aren't going to be a big threat to cryptocurrency mining or the cryptography that protects transactions until this problem is solved.
Efforts are being made to make hybrid quantum-classical computers as well as software that can lessen the noise caused by quantum noise. But that doesn't deal with another big problem quantum computers have to deal with.
It's very hard to fix mistakes on a quantum computer because of the linear nature of quantum computations. This makes it very hard to fix mistakes on a quantum computer. Checking qubits for errors could change their state or superposition, which could change the results.
Physicist Christopher Monroe and a group of researchers from the University of Maryland have made a lot of progress in quantum error correction. They came up with something called the Bacon-Shor code. Because of this type of error correction, a quantum computer with at least 1,300 qubits is expected to be needed. That's more than 10 times the number of qubits in IBM's Eagle computer.
As it stands, quantum computers may one day be able to do a lot of damage to crypto mining and the integrity of blockchain-based networks, but the current technology isn't advanced enough to cause any real worry.
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