Quantum Computers Need Far Less Power to Crack Crypto, Google Research Reveals

New research from Google shows that quantum computers could require far less power than previously thought to break the cryptography securing cryptocurrency blockchains. This alarming discovery accelerates the debate on the sector’s security and raises fundamental questions about the future of digital assets.

A Game-Changing Discovery

Research published by Google Quantum AI this Monday, March 30, 2026, reveals a major breakthrough in assessing quantum risks for cryptocurrency cryptography. According to Google’s scientists, a quantum computer could now break the cryptography protecting Bitcoin and Ethereum using fewer than 500,000 physical qubits.

This estimate represents a staggering 20-fold reduction compared to previous projections. Until now, the scientific community estimated that several million qubits would be needed to compromise the cryptographic algorithms used by major blockchains. This new finding challenges the traditionally accepted timeline for the arrival of what is known as « Q-Day. »

The qubit, the basic unit of quantum computers, has never been closer to being able to compromise the private keys of cryptocurrency users. This rapid advancement in quantum technology places the entire crypto ecosystem facing an unprecedented challenge.

Bitcoin Vulnerable in Just 9 Minutes

The theoretical scenario presented by Google is particularly alarming for Bitcoin holders. Under optimal conditions, a quantum computer could derive a private key from a public key in just 9 minutes, providing a window of opportunity for a so-called « on-spend » attack.

This attack becomes especially critical when considering that Bitcoin requires approximately 10 minutes to confirm a block. A sufficiently powerful quantum computer could theoretically crack a private key, sign a competing transaction, and steal funds before the legitimate transaction is confirmed in a block.

The 9 to 10 minute window is extremely narrow but entirely feasible for an attacker with a powerful quantum computer. This is why researchers describe this attack as « on-spend, » as it must be executed quickly after the public key is revealed during a transaction.

Justin Drake, co-author of the study and renowned Ethereum researcher, stated on X that his confidence in the arrival of « Q-Day » by 2032 had « significantly increased. » He now estimates at least a 10% probability that a quantum computer will recover a private key from an exposed public key by 2032.

Ethereum: A Structural Vulnerability Even More Concerning

While Bitcoin requires precise timing to be vulnerable to this type of attack, Ethereum presents an even more concerning risk profile. Google researchers warned against Ethereum’s structural vulnerability to « at-rest attacks, » which require no temporal synchronization.

This systemic vulnerability stems from Ethereum’s account model itself. The moment an Ethereum account makes its first transaction, its public key becomes permanently visible on the blockchain. Unlike Bitcoin where public keys are only revealed at the time of spending, Ethereum exposes this information permanently from the first interaction.

A quantum attacker could therefore take all the time needed to derive the corresponding private key, without any time pressure whatsoever. They could prepare their attack years in advance, silently accumulating public keys from the wealthiest accounts.

The figures advanced by Google are staggering: the 1,000 richest Ethereum accounts, collectively holding approximately 20.5 million ETH, could be cracked in fewer than nine days by a sufficiently powerful quantum computer. This vulnerability also affects other assets on Ethereum, including ERC-20 tokens and NFTs.

Implications for Digital Asset Holders

For the average cryptocurrency investor, this research raises legitimate questions about asset security. Unlike traditional banking systems where funds are protected by insurance and regulations, cryptocurrency cryptography is absolute. If a private key is compromised, funds are irrevocably lost.

Users who have kept their assets on « legacy » addresses are particularly at risk. These addresses, which were not designed with quantum threats in mind, rely on cryptographic primitives now considered vulnerable.

It is crucial to understand that the quantum threat is not limited to future transactions. It can also target public keys already exposed in blockchain history. Even a wallet that has never made a transaction could be at risk if its public key has been revealed by any means.

The Blockchain Ecosystem’s Response

Facing this growing threat, the crypto ecosystem is not standing still. Nic Carter, leading crypto entrepreneur and analyst, stated that elliptic curve cryptography (ECC) is now on the « brink of obsolescence. » He also noted that Ethereum already has solutions in development, while Bitcoin presents an approach qualified as « worst in class. »

This criticism refers to Bitcoin’s lag in adopting quantum protection measures. While Ethereum is actively working on its post-quantum roadmap, the Bitcoin community appears divided on the best approach to adopt.

The Ethereum Foundation published its post-quantum roadmap in February 2026, demonstrating anticipatory awareness. Vitalik Buterin proposed four major modifications that will need to be implemented to protect the network: validator signatures, data storage, accounts, and proofs will all need to be upgraded to protect against quantum threats.

These changes represent a considerable technical challenge. Upgrading a blockchain as complex as Ethereum requires years of research, development, and rigorous testing. The transition to post-quantum cryptography (PQC) must be carried out without compromising the network’s decentralization and security.

Google Sets 2029 Deadline: A Tight but Necessary Timeline

Google has set a strict deadline for migration to post-quantum cryptography: 2029. The search giant warns that the « quantum frontier » could be closer than it appears, urging the entire industry to accelerate preparations.

This 2029 deadline represents a significant shift from previous estimates that relied on a much more distant horizon. It reflects Google’s rapid progress in developing its own quantum capabilities, particularly with the Willow chip unveiled in December 2024.

The Mountain View firm recommends that blockchains transition to post-quantum cryptography now, rather than waiting for real threats to emerge. This proactive approach aims to protect users before quantum technology becomes an accessible reality for attackers.

What is Post-Quantum Cryptography?

Post-quantum cryptography (PQC) refers to a set of cryptographic algorithms designed to resist attacks from quantum computers. Unlike current algorithms like RSA or ECDSA, which rely on the difficulty of factoring large numbers or calculating discrete logarithms, PQC algorithms are based on mathematical problems believed to be impossible to solve even for a powerful quantum computer.

Among the promising candidates are algorithms based on Euclidean networks (lattice-based cryptography), error-correcting codes, and multivariate polynomial equations. The National Institute of Standards and Technology (NIST) in the United States has already standardized several PQC algorithms, including CRYSTALS-Kyber for encryption and CRYSTALS-Dilithium for digital signatures.

Migration Challenges

Migration to post-quantum cryptography will not be without obstacles. The process involves profound changes in blockchain infrastructure, often requiring « hard forks » or major protocol upgrades.

For users, this means that old keys and addresses will become obsolete. Every cryptocurrency holder will need to generate new keys using post-quantum algorithms and migrate their funds to these new addresses. This process will be particularly complex for lost assets or wallets whose private keys are no longer accessible.

Exchanges and other cryptocurrency custody services will also need to update their systems to support the new algorithms. This transition could take years and require unprecedented coordination within the industry.

Impact on the Cryptocurrency Market

Google’s announcement naturally impacted the market. Bitcoin and Ethereum prices experienced increased volatility in the hours following the study’s publication, testifying to investor concern about this threat.

However, analysts point out that this awareness is ultimately positive for the ecosystem. Precisely quantifying the risk now allows the industry to plan and allocate the necessary resources for an orderly migration.

Some see this as an argument in favor of Ethereum over Bitcoin. Ethereum’s structure, while vulnerable to at-rest attacks, has a clear roadmap for post-quantum protection. Bitcoin, on the other hand, faces unique challenges related to the nature of its addresses and its community’s conservative development approach.

Conclusion

Google’s research marks a turning point in assessing quantum risks for the crypto ecosystem. With a 20-fold reduction in resources needed to break cryptography, the time window before Q-Day is narrowing significantly.

For investors and developers, this study should serve as a call to action. The transition to post-quantum cryptography is no longer a question of « if » but « when. » Blockchains that respond quickly will be best positioned to preserve the security of their users’ funds.

The future of cryptocurrencies depends on the industry’s ability to anticipate and adapt to this new technological reality. The countdown has begun, and every passing day makes migration more urgent. Sector players, from developers to investors, must now consider the implications of this threat and prepare accordingly.

The good news is that solutions exist and the ecosystem has time to implement them correctly. But this time is not unlimited, and the coming years will be crucial in determining whether cryptocurrencies can survive the quantum era.