Could Quantum Computing Kill Blockchain?

We’re lucky to be alive today. We are in the midst of an immense technological upheaval, one where our invention and discovery, driven by socially minded scientific research, is creeping into every aspect of our lives. Blockchain is only one of these technologies; others such as quantum computing and clean energy are making equal headway in the pursuit of a better world.

Scientific discoveries often have a way of testing each other, in a sort of technological survival of the fittest. For instance, when clean energy regulations mandate the reduction of traditional energy producing industries, blockchain must design solutions to reduce energy consumption while continuing the creation of new blocks in the chain. As the blockchain lengthens, the electricity and computing resources requires increase exponentially.

The Threat of Quantum Computing to Blockchain

Quantum computing gives us extraordinary computational power, making mince meat out of problems classical computers struggle to solve. The world’s most pressing issues, like that of climate change, can only be overcome with machines like quantum computers. Yet, as with all new technologies, it has the power to render features of other technologies obsolete. These technologies must mutate to survive and thrive, or else be left in the junkyard of one-hit wonder technologies.

With blockchain, that predator is quantum computing. Blockchain’s security comes from its enhanced encryption standards, but the power of quantum computing leaves experts worried that the encryption employed by blockchain will be overcome too easily by quantum computing.

Recently, researchers from the University of South Wales constructed a new architecture, similar to the ones used in today’s processors, to perform quantum calculations. This has significant implications for the average person. It means that the same technology used to run the devices you use today could be used to run quantum computing calculations.

Quantum computing, even pocket quantum computing, is inevitable. However, it has always been seen as a distant dream – 10 to 15 years in the future has been the industry opinion on the arrival of commercial quantum computing. This discovery by UNSW researchers discredits that prediction. It could now arrive much faster and that may not bode well for cryptography and blockchain as a whole.

It is technically possible for a classical computer to break through the asymmetric encryption that coins like Bitcoin use, using sheer brute force (running through all possible solutions); it would just take a very long time. Quantum computers operate at a magnitude many times quicker than classical computers though, and it is easier for it to defeat asymmetric encryption.

That puts cryptocurrency and blockchain in a tight spot. Cryptocurrency and blockchain could be forced to evolve, to mutate so as to possess new characteristics, or else the much-loved security and privacy that enthusiasts sing praises about might be a thing of the past.

However, all is not lost. Coin developers have an eye for the long-term future, perhaps because cryptocurrency itself is only in the toddler stage. There is a long way to go before cryptocurrency matures into worldwide use. Developers are careful to plan for any obstacles that might occur and this includes quantum computing.

But before we talk about the possible solutions that blockchain could use in defense against quantum computing, let’s take a look at what quantum computing is. Like blockchains and cryptocurrency, it’s useful to know a little about a technology that is going to have an unprecedented impact on our lives.

Making the Universe Work for Us

Quantum computing is the end-game of computing research. It is surpassed in awe and speculation by only one other field of research – Artificial Intelligence. For many years, organizations like NASA and industry giants like Google have been pouring their resources into the perfection of this crazy field of physics for everyday use.

For now, it is limited to high-tech research labs and a select few organizations but, at one point, so was the traditional computer you use today. The smartphone in your hand is many times more powerful than the Voyager spacecraft that now floats in interstellar space and the computers that simulated nuclear warfare during the Cold War. It is only a matter of time before quantum computing becomes more accessible to the average person.

Today’s computers use bits. These are values that can be either 0 or 1. By itself, it doesn’t amount to much, but when you combine these “yes” or “no” values with other “yes” or “no” values repeatedly, you can come up with answers to really complex questions (In fact, you only need 6 bits to figure out what a letter is – though in practice, it takes 8 bits.) That’s pretty much all that your computer needs to do everything it does today.

Complex CGI rendering? Check. Video games? Check. Possible ultra-realistic simulations of the world? Check. All of this can be done with just bits.

Quantum computing takes this idea to a whole new level. Incredibly, it harnesses the very fabric of the universe to do this. The quantum computers that are operational today manipulate the universe and parallel universes to make calculations.

Quantum computers run on qubits, which can exist in the state of 0 and 1 simultaneously. We won’t go into the details, but with each additional qubit, the computing power of the computer grows exponentially. This allows the quantum computer to carry out complex calculations at a speed that far outpaces today’s computers, reducing the time to solve complex mathematical models, simulations and cryptographic security.

How Encryption Works Today

The most popular cryptography technique used today is public key cryptography. This uses a pair of public and private keys to encrypt and decrypt messages (or transaction data, in the case of blockchain) to ensure that only verified users can access the information.


In a nutshell, your public key is used to access the encrypted message and your private key is used to decrypt the message. The strength of the private key depends on the security methods and the secrecy of the private key. Blockchain uses digital signatures for additional protection.

This form of cryptography has been in use for many years and it is a testament to its efficiency that it has stood up against decades of attempts to break it.

Theoretically, quantum computers can easily solve the security methods of asymmetric cryptography. The quantum computer just has to be big enough, and the industry is making leaps and bounds with regards to this.

It is estimated that it will take 4,000 qubits to break the strongest encryption standards of today. In November 2017, IBM announced that it had just manufactured a 50-qubit quantum computer. That may seem like it’s a long way off from 4,000, but remember, technology doesn’t grow in a linear fashion. The time between milestones shorten quickly as time progresses. It was 50 years before computers went from giant military contraptions to household items. It’s only been 35 odd years since then and we’re already well on our way to the next age of computing.

To summarize, today’s encryption standards in blockchain work at the moment, but quantum computing is right on its tail. What does that mean for blockchain and cryptocurrencies?

Could Quantum Computers Kill Blockchain?

If quantum computing research continues at its current pace, then it will have no problem breaking the encryption used by blockchain. The economic system of cryptocurrencies would become all but useless since it would be possible for hackers to steal your coins, commit fraud and control the blockchain. If someone could easily steal your bitcoins, it wouldn’t be good for Bitcoin’s reputation.

You may have heard of the term “51% attack”. This is when miners control over 50% of the network, allowing them to double spend. In layman’s terms, this means they can spend money twice by deleting transactions from the blockchain.

Quantum computers could give malicious miners the power they need to break this 50% threshold. This particular security worry is not an immediate concern. The projection is that it will be at least 10 years before quantum computers are capable of doing this. However, with the recently revealed engineering architecture for quantum computers, that timeline may be shortened.

There is a far bigger concern which, as we mentioned, is the ease with which quantum computing can break public key encryption. Quantum computing is expected to reach this level of power by 2027. In other words, if today’s encryption standards and by extension, blockchain security, doesn’t evolve new security techniques or encryption standards, it will be practically useless.

The good news is that long-term thinking developers of cryptocurrencies are in fact preparing for this eventuality and they’ve got a few tricks up their sleeve.

Employing Preventive Measures

Cryptocurrencies are employing a variety of tools to combat the fast approaching threat of quantum computers. It’s a technological evolution that’s shaping up to be quite a show.

One of these developments is an upgraded version of Bitcoin called qBitcoin. It is conceivable to utilize quantum cryptography protocols, such as the BB84 quantum key distribution scheme, to transfer these qBitcoins between users.

There’s an irony here: the very same technology that quantum computing uses to threaten blockchain security, the qubit, is used to protect blockchains. Unfortunately, there are hurdles involved in this method. It would be necessary to install a quantum distribution network to transfer these qubits, which is financially infeasible on a large scale because of the high cost of construction. With time, however, it may become cheaper.

Another proposed method is the Quantum Resistant Ledger, developed by Dr. Peter Waterland. This new technique was designed with post-quantum cryptography in mind. It aims to combat the threat of quantum computing by implementing new digital signatures into transactions, one that makes the ledger resistant to quantum computation.

Using a Proof-of-Stake algorithm, this method has been proven to have secure hash-based pseudo-random functions that immunize against quantum analysis. Unlike qBitcoins, it does not need expensive infrastructure to operate. It can run on low-power devices like laptops and Raspberry Pis.

The QRL also plans to introduce a quantum-secure messaging layer. Through a technique called lattice-based cryptography, transactions will be signed with a special public key that can be used by users to dial up a secure communications medium across which messages can be sent. Additional plans include linking blockchain IDs to these quantum-secure addresses, called XMSS transactions.

There are also existing cryptocurrencies that are planning for post-quantum cryptography. IOTA, one of the biggest coins on the market, uses Winternitz OTS or Lamport Signatures to secure its signatures from quantum analysis. The only issue with this is that each address can only be used once.

IOTA’s proprietary protocol, Tangle, counter-intuitively, actually speeds up the network as more users arrive. IOTA’s Directed Acyclic Graph, different from a blockchain, is a noteworthy new development in cryptocurrency technology. On this network ,the sender of the transaction must verify two other transactions. This is fascinating new protocol and is well worth a read.

What’s the Prognosis for Blockchain Security?

Not too worrisome, fortunately.

Yes, quantum computing could potentially spell disaster for cryptocurrency but the industry is already taking up arms against this threat. It’s still very early in the lifespans of both technologies and it may even aid them both on the whole if they compete side by side. The imminent arrival of quantum computers is forcing encryption and cryptocurrency experts to prepare for it, which only improves its features and chances of survival.

The answer is then that you don’t have to panic. It may happen that quantum computing wins, but the preemptive efforts of cryptography and cryptocurrency experts look promising. In my personal opinion, it doesn’t seem like quantum computing will destroy the market. Blockchain’s inherent value in so many industries is a boon that must be taken with both hands. It’s hard to imagine anyone wanting to let it go. It seems likely that some defense against quantum computing will be discovered or invented before long.


If you’ve got your own thoughts about quantum computing, blockchain security or coins that are tackling the problem of post-quantum cryptography, please let us know in the comments below.