After announcing a 2029 target for migration to post-quantum cryptography (PQC), Google issues a new warning that a quantum system could attack a Bitcoin (BTC) transaction in about nine minutes.
The tech giant warned it won't happen today but it's a possibility one should be prepared for sooner than later.
Related: Google reveals major 2029 quantum threat for digital wallets
Understanding quantum threat to cryptocurrency
Cryptocurrencies are virtual currencies that rely on cryptography to encrypt or conceal sensitive financial details from those other than transacting parties.
Though the most powerful supercomputers active today will take thousands of years to decrypt cryptography, the cryptocurrency community fears quantum computers will be able to crack cryptocurrencies like Bitcoin within minutes or even seconds.
While the computers active today use binary electrical signals or bits to represent ones or zeros, quantum computers use quantum bits (qubits), which are subatomic particles.
Optimized qubits can simultaneously represent combinations of both ones and zeros. More qubits mean large-scale computing power for problem-solving.
It was in the 1990s that the Massachusetts Institute of Technology (MIT) mathematician Peter Shor developed the first well-known quantum algorithm to crack encryption. Over decades, quantum computing has seen enormous progress.
More on Quantum Computing:
Google warns of quantum threat to cryptocurrencies
On March 30, Google published a new whitepaper in which researchers explained that most cryptocurrencies depend on the 256-bit elliptic curve discrete logarithm problem (ECDLP-256) to secure wallets and transactions.
The paper found that it could take fewer than 500,000 qubits—far less than millions of qubits cited earlier—to crack the cryptography used by cryptocurrencies like Bitcoin or Ethereum (ETH).
"This is an approximately 20-fold reduction in the number of physical qubits required to solve ECDLP-256."
Here is how grave Google estimated the threat to be.
Instead of going after old wallets, a quantum hacker could target real-time Bitcoin transactions. When a Bitcoin transaction is made, the public key is revealed for a brief period. A powerful and fast quantum computer can use the public key to arrive at the private key and steal the money.
Such a quantum computer could be prepared to launch the attack in advance by making necessary calculations and then crack a Bitcoin transaction in about nine minutes, the paper warned.
It takes approximately 10 minutes for a Bitcoin transaction to confirm; the probability of success is slightly less than 41%, the paper estimated.
In fact, around 6.9 million Bitcoin are already vulnerable, including around 1.7 million coins from the Satoshi era, the paper highlighted.
Though the Taproot upgrade in 2021 claimed to make Bitcoin private and efficient, it exposed public keys by default. That choice could expand the number of vulnerable Bitcoin wallets, the paper concluded.
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Cryptocurrencies like Ether take far less time than Bitcoin to confirm transactions, so they are less vulnerable to such attacks, it concluded.
Google used the zero-knowledge proof method to conduct the research so that the methodologies used to crack cryptography aren't used by bad actors.
The tech giant said it has been working since 2016 to migrate to PQC and urged all vulnerable cryptocurrency communities to join the migration without delay.
Related: Elon Musk reveals 'plus side' of quantum computing breaking Bitcoin
Expert warns quantum threatens entire crypto industry
Chris Tam, president of the quantum technology company BTQ Technologies, told TheStreet Roundtable that the estimates for quantum computing breaking cryptography have only lowered over the years. The Google whitepaper also mentions a 20-fold reduction in the number of physical qubits required to solve ECDLP-256, he reminded.
We are seeing rapid progress in the field and this won't be the last breakthrough for a while, he added.
Though a transition to post-quantum (PQ) algorithms can save cryptocurrencies from future quantum threats, it's not going to be easy, Tam underlined.
Crypto networks, decentralized by definition, don't update with the "flip of a switch" and networkwide backward compatible upgrades require months, if not years, to be properly implemented, he warned.
"Networks can and should put plans in place to address not only the risk, but the entire migration effort that will be required."
Decentralized networks have a path to follow: discourses, proposals, and testnets. If the social consensus is slow to adopt or fails, even forks are in the cards, he predicted.
Tam gave the example of Bitcoin Quantum, a quantum-safe fork of Bitcoin that BTQ Technologies is testing with quantum-safe features.
TheStreet Roundtable asked Tam whether the market estimates for PQ crypto are incentive-driven as large amounts of funds pour into research. He disagreed.
Experts aren't hyping PQ crypto, Tam underlined but added, "Anyways, the thing with crypto is that there will always be perverse incentives."
But the threat is real and the crypto industry needs to be prepared.
"If we look at this scientifically, there's no doubt that quantum threatens the entire industry and progress is moving faster than ever."
Bitcoin was trading at $68,073.72 at press time.
Related: Michael Saylor has a harsh response to quantum computers breaking encryption
This story was originally published by TheStreet on Apr 13, 2026, where it first appeared in the MARKETS section. Add TheStreet as a Preferred Source by clicking here.
