As quantum computing advances, the cost of attacking Bitcoin may drop dramatically.
In a new analysis, Google has warned that cryptocurrencies such as Bitcoin and Ethereum may be more vulnerable to attacks than previously thought.
The learning shows that a quantum machine running Shor’s algorithm can solve the 256-bit Elliptic Curve Discrete Logarithm Problem (ECDLP) for securing many blockchains with few qubits and gates.
Google researchers estimate that 1,200-1,450 logical qubits and 70-90 million quantum gates can break Bitcoin’s 256-bit encryption in minutes, executable at less than 500,000 physical qubits per minute.
These results suggest that quantum attacks may occur much sooner than previously predicted.
Bitcoin wallets in danger
Bitcoin’s future risk depends on hardware scales first, according to Google. Fast systems can allow for long-term attacks during trading, while slower systems can track savings.
As seen in this paper, the main vulnerabilities include reusable addresses, old wallet models, and the exposure of public keys during transactions, where millions of BTC are at stake.
An “On-spend” attack, which is seized and used before verification, can be possible within a Bitcoin window of 10 minutes. This refutes the long-held view that transaction fees and network speed can provide sufficient protection against quantum adversaries.
Billions of sleepers are at risk
Apart from action, the main target is expected to be accommodation.
According to researchers, about 1.7 million Bitcoin, worth billions of dollars, are locked when they first use a wallet called P2PK, many of whom believe that it is impossible because the keys are lost.
This property cannot be changed to anti-quantity standards and can eventually be opened by anyone with access to critical computing resources, or CRQC.
This creates what experts describe as a “permanent blessing” for future attackers, from government actors to private companies, and enforcement can be difficult in the global system.
Mines are safe, although not completely
Although quantum computers could threaten Bitcoin’s cryptography, Google says that the mining itself is not immediately at risk. Quantum speed from Grover’s algorithm is low, and ordinary ASIC miners are still in control.
However, sudden attacks can disrupt the Internet economy. A successful mass attack can weaken Bitcoin’s value, reduce miners’ incentives, and disrupt operations and security.
Taproot’s update improves privacy but exposes Bitcoin to mass attacks
Google warns that Bitcoin’s cryptographic records can be targeted by quantum attacks.
Funds are managed via UTXOs, public keys, and digital signatures, allowing for transparency in high-risk transactions.
The original and Taproot addresses are mostly visible, while the default addresses keep the security until they are used.
The report says that Taproot represents a balance between functionality and security and introduces P2MR as a future version of the script designed to preserve the benefits of Taproot and reduce the risk of proliferation.
37 million ETH are at stake
Quantum computing could affect Ethereum more than Bitcoin, according to Google.
Smart contracts do not have post-quantum cryptography, making code at-rest vulnerable, while BLS signatures in Proof-of-Stake create systemic threats if a sufficient number of validators are compromised.
The Ethereum layer 2 network also relies on KZG’s insecure promises, which can allow permanent gateways.
Effective decentralization requires greater coordination, manual upgrade of contracts, faster key exchange, and transition to post-quantum cryptography across the universe.
Beyond Bitcoin and Ethereum
Quantum vulnerabilities extend beyond Bitcoin and Ethereum, affecting forks, sidechains, cryptocurrencies, and stablecoins, Google’s core values.
Many chains still rely on ECDLP-based cryptography, leaving money and privacy in the open, while bridges with multiple signatures and admin keys create additional risks.
Even blockchains that maintain privacy such as Zcash or Mimblewimble can face the risk of reversals, which facilitate the transparency of past transactions or inflation.
A complete transition to post-quantum cryptography (PQC) is possible
Blockchain platforms are increasingly hosting real-world transactions, including bonds and real estate. Estimated to be a market of more than $16 trillion by 2030, experts warn that cyber threats could become a threat to the entire economy.
While short-term mitigations, such as greater flexibility and protocol changes, may reduce exposure, moving to PQC alone will provide permanent protection from emergency threats, Google notes.
A complete transition to post-quantum cryptography is possible, but if the process starts now, Google researchers emphasize.
New cryptographic methods, including lattice- and hash-based systems, are already being tested and released in selected networks.
Some projects, such as QRL and Abelian, were built to avoid crowding from the start, while others, such as Algorand, Solana, and the XRP Ledger, are trying to integrate quantum security. The Ethereum Foundation has also increased its efforts to improve the foundation of post-quantum security.
Google encourages crypto people to prepare for mass attacks early, take PQC, fix short-term vulnerabilities, and share information to protect funds and public trust.
