Quantum computing and blockchain are both at the very cutting edge of technology. However, these two technologies are sometimes misconstrued. Blockchain networks are highly secure computing network, which allow for transparency and underpin the likes of cryptocurrencies. Quantum computers, on the other hand, can process data much more efficiently than regular computers. As such, quantum computers are theoretically capable of advanced computations so complex that they were previously impossible. Although quantum computing is in its infancy, it can raise safety questions about the security of proof-of-work (PoW) blockchain networks and cryptocurrency protocols such as Bitcoin. Accordingly, many investors are wondering, “to what extent is quantum computing a threat to Bitcoin?”.

In this article, we’re going to dive deep into the world of quantum computing and blockchain. We’ll be asking some of the most pressing questions surrounding these subjects, such as, “what is quantum computing?” and “is quantum computing a threat to Bitcoin?”. Also, we’ll look at the types of vulnerabilities that could occur, the likelihood of a quantum attack on the Bitcoin network, and what the blockchain community can do to safeguard against any potential threats in the future.

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Quantum Computing and Blockchain

So, to what extent is quantum computing a threat to Bitcoin? To fully understand the differences between quantum computing and blockchain, and assess the potential risks, let’s take a closer look at each of these revolutionary technologies.

What is a Blockchain?

A blockchain is a type of distributed ledger technology (DLT) that acts as a public database or ledger of transactions. Blockchain is the underlying technology of cryptocurrency networks such as Bitcoin. It provides a permanent, immutable record of data and events in a digital format. Once a miner adds a transaction to the blockchain, nobody can change or alter it. This allows for a decentralized record of transactions without the need for intermediaries or a central point of authority.

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Blockchains store transactional data in blocks. Each block has a predetermined size that limits the number of transactions it can contain. Once a block is full of transactions, it is permanently etched into the blockchain. Also, instead of storing all data on a single server, blockchain data exists across an entire network. Plus, each block interlinks with every previous block in the chain.

Every node in the network has a copy of the same ledger. Furthermore, there needs to be a framework set in place to enable each node to agree on the legitimacy of each transaction. For this, blockchain networks use a consensus mechanism. For example, the Bitcoin blockchain uses a consensus algorithm called proof-of-work (PoW). Special nodes called mining nodes compete to solve a complex mathematical puzzle by expending electricity. The first miner to solve the puzzle earns the right to validate a transaction and add it to their block. In return, the miner receives Bitcoin block rewards.

Bitcoin mining requires expensive equipment and ongoing electricity costs. Miners trying to defraud the network can lose the block rewards they would otherwise receive for their “work”. Accordingly, consensus mechanisms keep blockchain networks secure and make it easy to spot potential attacks. The network can easily detect anyone who tries to spend Bitcoin twice or process an illegitimate transaction.

Blockchain Security

Every block appended to the blockchain is interlinked with the previous block. This means that any potential attacker would have to alter every transaction in every block before they can manipulate any specific transaction. Also, any potential attacker would need at least 51% of the computational power of the entire network to attack a PoW blockchain. Plus, if a hacker did achieve this, they could only alter one transaction before reattempting the hack to falsify another. Thus, it’s more economically viable to be a cooperative node than to attack the network.

For large PoW blockchains such as Bitcoin, the threat is minimal because of the time and cost of an attack. However, smaller PoW blockchains are more susceptible to 51% attacks. The smaller the blockchain network is, the less computational power a bad actor needs to carry out a 51% attack.

What is Quantum Computing?

Quantum computing is an advanced technology that uses the laws of quantum mechanics to solve problems that are too complex for standard computers. Quantum theory describes the behavior of energy and materials on an atomic and subatomic level. Classic computers can encode bits of data that have a value of one or zero. This often makes them restrictive when it comes to solving complex problems with a lot of variables. However, quantum computing solves this by using quantum bits (qubits), the basic unit of quantum measurement.

Quantum computing benefits from the ability of subatomic particles to exist in multiple states simultaneously (i.e., both one and zero). As quantum computers create and process more qubits, they become exponentially more powerful. On the other hand, classic computers increase in power linearly with the addition of more transistors.

Furthermore, quantum computing helps scientists and engineers to solve extremely complex problems. For example, quantum computing can be applied to the behavior modeling of individual atoms in a molecule. Also, it can be used for mapping out logistical routes in global shipping networks. 

Quantum computing gives scientists the ability to solve problems that were previously thought to be unsolvable. Using the principles of superposition and entanglement, quantum computers can execute computations substantially quicker than traditional computers, using much less energy. 

This technology has become widely used in finance, intelligence, military, aerospace design, digital manufacturing, and nuclear fusion. Some of the largest technology companies in the world are entering the quantum computing field. This includes Microsoft, IBM, Google, Intel, Alibaba, and HP.

Is Quantum Computing a Threat to Bitcoin? 

Now, let’s consider the question, “is quantum computing a threat to Bitcoin?”. When a node tries to defraud a PoW blockchain such as the Bitcoin network, it must first attempt to solve a complex math puzzle to earn the right to validate a transaction. This is what we call a “hash function”. Once a node solves the puzzle and earns the right to validate a transaction, it can attempt a “double-spend”, meaning an attempt to spend the same Bitcoin or token twice. 

Most PoW blockchains have a built-in security feature that only allows nodes to try and solve one math problem one guess at a time. Each guess requires significant energy expenditure (for large blockchain networks) and prevents nodes from trying to validate other transactions at the same time. However, quantum computing could put this security measure in jeopardy. 

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Unlike regular computers, quantum computers can effectively make multiple attempts at finding the hash simultaneously. Also, quantum computers are particularly effective at cracking passwords and solving cryptographic problems. That said, these next-gen computers are still a long way from being capable of carrying out such attacks. A significant amount of development will need to occur before quantum computers can carry out such complex tasks. Quantum computers are extremely expensive to design and build, making them inaccessible to most potential hackers. In addition, the linear nature of quantum computations makes error corrections incredibly difficult and time-consuming. Plus, checking qubits for errors can skew computation results.

Despite this, several developers are implementing quantum-proof coding, also known as post-quantum coding, to address the potential vulnerabilities blockchain networks could face as a result of the advancements in quantum computing. This helps to strengthen the elliptic curve encryption of digital signatures across public blockchain networks and safeguard against quantum attacks.

The Problem with Quantum Computing and Blockchain

Now, you may be wondering, “to what extent is quantum computing a threat to Bitcoin?”. According to an article published by TechRadar in February 2022, scientists from the University of Sussex predict that a quantum computing system would need approximately 13 million qubits to break the SHA-256 cryptographic algorithm underpinning the security of the Bitcoin network within 24 hours. Researchers also predict that a quantum computer with 317 million qubits would be needed to break the Bitcoin code within an hour and 1.9 billion qubits to accomplish it in ten minutes.

The study went on to suggest that a fork of the Bitcoin code into a quantum-safe encryption system is likely to be implemented before any significant threat is apparent. Also, a quantum computing system would need to be geared specifically towards the task of attacking a blockchain network. The mere ability to process complex computations quickly and efficiently poses little threat to Bitcoin in and of itself. Despite this, developments in quantum computing raise important questions about the security of current cryptography methods.

Currently, quantum computers function with around 127 qubits. Also, the most powerful quantum computers are not easy to replicate. However, the rate of development in the field of quantum computing suggests that this could be a reality in the near future. If a hijacker is able to carry out a successful 51% attack, the entire Bitcoin network would be in jeopardy. Contemporary hardware is a long way from being able to achieve this, but the situation is almost certain to change in the years to come.

Could Quantum Computing Break Bitcoin?

Another potential threat to the Bitcoin network and other PoW blockchains is the use of quantum computers to speed up the mining process. Again, this technology is a long way from being available. However, this could pose a significant security risk if someone can expedite the rate at which Bitcoin or other cryptocurrencies enter circulation. Also, a centralization of hash power could make a 51% attack easier to pull off. So, in answer to the question of “is quantum computing a threat to Bitcoin?”, that which poses little threat today may prove to be a significant threat tomorrow.

Quantum Computing and Blockchain – Summary 

On paper, quantum computing has the potential to jeopardize blockchain security. However, the technological advancements necessary for this to be a real-life issue are seemingly still many years. Nevertheless, quantum computing could theoretically allow for machines that are powerful enough to break the Bitcoin network.

With this in mind, many blockchain developers have begun mapping out post-quantum roadmaps. Also, regulators are keen to explore safeguarding measures to limit the abilities of quantum hackers. That said, the advent of quantum computing poses a real threat to the security of blockchain networks. Developers must ensure they keep up with the changing times to reduce these potential security threats from quantum computing. What’s more, protocols could need to implement post-quantum coding before significant threats emerge.

Both the quantum computing and blockchain field are developing at breakneck speed. As such, it’s difficult to say for sure whether blockchains are currently safe against quantum attacks. Nevertheless, if the crypto community adopts safeguarding technologies built to prevent these attacks, the immediate threat posed by quantum computing will remain low. This is especially important as cryptographic security is at the heart of the Web3 industry. It’s also worth taking into account that the crypto history books are filled with technological hurdles that have already been overcome. As such, few communities are as well-equipped for the threat of quantum computing attacks as the blockchain community. 

To learn more about threats to the Bitcoin blockchain, check out the Bitcoin Vulnerabilities course at Moralis Academy. In addition, check out the Ethereum Smart Contract Security course to learn how to protect against smart contract hacks! Kickstart your blockchain education today with Moralis Academy. Also, check out our “Why to Learn Web3 Development” and “Crypto Backed by Gold” articles to further expand your blockchain knowledge!