Experts say that ultrapowerful quantum computers could eventually crack the security codes of blockchain, the underlying technology for Bitcoin. That would be a hacker’s dream. And it could deal a severe blow to investors’ trust in the $2 trillion-plus market for the leading cryptocurrency.
Roughly a quarter of all Bitcoins are now protected with algorithms that could be cracked by quantum computers in five or 10 years, Gartner analyst Avivah Litan tells Barron’s. Those are mostly older Bitcoins housed in digital vaults, or wallets, that date back as far as 15 years.
As quantum computing keeps advancing, the damage could spread to newer wallets, and then to the market’s broader structure. The computers “might eventually become so fast that they will undermine the Bitcoin transaction process,” experts at Deloitte have written. Conceivably, hackers could start rewriting the history of trades.
The crypto industry knows about these risks and is quietly preparing to defend itself.
“There are very strong incentives to protect the value in Bitcoin’s network and drive the development of quantum-resistant technology,” Litan says. Ultimately, the industry’s best weapon for the fight could prove to be quantum computing itself. Some firms are already working on that.
The big, unanswerable question is how quickly quantum develops. That is, how soon might the security features of blockchain meet their match? Will the industry finish its preparations in time?
Of the two technologies, blockchain is the easier to understand. It is essentially a digital record-keeping system consisting of “blocks,” each containing details on validated transactions. Each time an entry is created and authenticated, a block is added. It is the beating heart of the Bitcoin market.
The concept of a blockchain has existed since the 1990s, when computer scientists Stuart Haber and W. Scott Stornetta proposed the first system to timestamp data using cryptography. In October 2008, a mysterious, faceless developer (or developers) going by the name Satoshi Nakamoto published a white paper detailing a “peer-to-peer electronic cash system” that would become the prototype for the blockchain network.
As it happens, Nakamato’s holdings—which the most bombastic estimates place at 1.1 million Bitcoins, or some $128 billion—could be vulnerable to the first wave of any quantum-based attacks. That’s because the assets are believed to have been tucked away since 2010 in the kind of older, digital vaults considered to be most at risk.
Quantum computing, under development since the 1980s, is derived from quantum mechanics. And what is that, exactly? The pioneering physicist Richard Feynman may have put it best: “I think I can safely say that nobody understands quantum mechanics.”
The remark, part of a lecture at Cornell University in 1964, drew chuckles from the audience, but the sentiment still rings true today, even as hype about the technology explodes on Wall Street. A collection of small, volatile quantum-computing stocks have become some of investors’ favorite speculative playthings.
In general, quantum computing aims to take traditional computing to an entirely new level. It seeks to solve big, complex statistical problems by examining large numbers of variables at the same time.
A typical quantum system consists of a bulky, refrigerator-like shell encasing a nest of hardware. At its core sits a quantum processor, usually no bigger than a thumbnail. Information is encoded by quantum bits, or “qubits,” which are created by manipulating and measuring subatomic particles like electrons, photons, and ions.
Because qubits allow these particles to exist in multiple states at once, quantum computers can perform calculations outside the reach of traditional machines. Theoretically, they can be used for everything from unsnarling a city’s traffic jams to discovering new treatments for cancer. And for cracking cryptographic algorithms.
“That is one of the cases where the features of quantum mechanics are used to do things that are very hard or too time-intensive—and basically impossible—otherwise,” says Thomas Ehmer, co-founder of the Quantum Interest Group at Merck KGaA.
To attackers, it’s the “holy grail,” Ehmer says. Quantum computers, he adds, could work in a “hyper-efficient” way to peel away the layers of numbers that form the core of blockchain encryption.
For most cryptocurrencies, that core is based on pairs of keys—a public key and a private key, which are mathematically linked. The public key is used for encryption, or scrambling data to safeguard it from prying eyes, while the private key is used for decryption, or converting it back into a readable format.
Think of a public key like an email address or a username. Anyone can view and share it, and anyone can use it to encrypt data. However, only the holders of the corresponding private key can decrypt the data. The security of encryption relies on the difficulty of factoring large numbers, or breaking a number into smaller prime numbers that, when multiplied together, equal the larger number. Current technology is unable to do that, but a fully realized quantum computer theoretically could, and in surprisingly short time.
“It’s like having a superpower that lets you quickly pick a lock that would take a normal person millions of years to even attempt,” Ehmer says.
There have already been attempts to crack the code. In a 2024 paper, Chinese scientists claimed they had used a system from D-Wave Quantum to break RSA encryptions, which are used in online banking transactions and VPN connections. The experiment, however, was conducted on a relatively small scale and wasn’t considered a major advance.
Still, fear is clearly seeping into the crypto industry’s consciousness. BlackRock, the world’s largest asset manager, warned of the advent of more powerful computers when it prepared to launch a Bitcoin exchange-traded fund in 2024. The firm noted in a filing with the Securities and Exchange Commission that “quantum computing could result in the cryptography underlying the Bitcoin network becoming ineffective, which, if realized, could compromise the security of the Bitcoin network” and lead to losses for shareholders. Similar language appears in BlackRock’s filings as far back as 2023.
Just how real is the risk? Some three-quarters of Bitcoins have an additional layer of cryptography that keeps them out of imminent danger. However, the threat is nothing to scoff at, according to Michael Osborne, chief technology officer at IBM Quantum Safe.
“Assets can be stolen from existing wallets if fairly simple actions are not taken to protect them,” Osborne says. The most immediate fix may be to move funds from old or reused addresses to new wallets that don’t have their public keys exposed, in anticipation of the day quantum computers gain the ability to determine a private key using a public key.
As quantum develops in the coming years, protective measures may well become harder to devise. Hackers could gain the tools to disrupt Bitcoin mining and the basic operations of the market, such as rewriting transaction history. Gartner’s Litan says that some experts place the odds of this happening at 50% by 2037.
“There is strong consensus in the Bitcoin community that preparation now is essential to prevent future catastrophe, though some view the threat as overhyped,” Litan says.
No matter the difference of opinions, developers aren’t sitting idly by. Rather, they have kicked off a digital arms race even before the true conflict has begun.
“It’s pretty widely known that the bad actors will try to use quantum computers to break classical encryption,” Quantinuum CEO Rajeeb Hazra tells Barron’s. “But that same tool can also be used to create better algorithms.”
The child of Honeywell Quantum Solutions and a United Kingdom–based start-up, Quantinuum was created through a merger in 2021. The firm received an initial investment of $300 million from Honeywell International, and released its first product—a random-number generator with cybersecurity applications—in December of that year.
In March 2025, Quantinuum teamed up with researchers at JPMorgan Chase for an experiment demonstrating how a quantum computer could best a classical machine at a random-number-generation problem. As random numbers are used in everything from computer simulations to cryptography, the study had important real-world implications.
“Forever the race will remain, right?” Hazra says with a chuckle. “We see it in the classical world, and we’ll see it taken to the next level with quantum.”
Researchers at D-Wave Quantum have approached the challenge by developing a blockchain architecture that runs on quantum computers. “The distributed nature of the Bitcoin network is based on a bunch of miners collaborating and each doing a hard cryptographic puzzle, which requires a lot of classical computational power,” explains Trevor Lanting, D-Wave’s chief development officer.
Blockchains rely on hashing, a mathematical function that acts like a digital fingerprint by converting an input into a string of characters. Hashing is used to encrypt transactions, and “proof of work” algorithms validate those transactions. D-Wave aims to replace this process with a quantum proof of work, which the company describes as a new way to securely and efficiently create hashes.
In a preprint submitted to research-sharing platform arXiv in March, scientists showed how they had tested a prototype blockchain on four D-Wave processors scattered across North America, “demonstrating stable operation across hundreds of thousands of quantum hashing operations.”
The race is far from over. Insights from IBM suggest cryptographically relevant quantum computers could arrive in a decade, while some organizations anticipate it may take up to 12 years to become quantum-resistant.
There’s an expression in the crypto community that might be appropriate here: “HODL,” or hold on for dear life.
Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com
