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Google Quantum AI reported that breaking the secp256k1 elliptic-curve cryptography used by Bitcoin, Ethereum, and other cryptocurrencies may require far fewer quantum resources than previously estimated. In a new whitepaper co-authored with researchers from the Ethereum Foundation, Stanford, and UC Berkeley, the team said an attack could need fewer than 500,000 physical qubits rather than the millions often cited, with optimized circuits using roughly 1,200 to 1,450 high-quality logical qubits. Under idealized conditions, the research suggests a primed attacker could recover a private key in about nine minutes, making an on-spend attack against a Bitcoin transaction theoretically possible within the network’s typical 10-minute confirmation window.
The paper warns that Bitcoin’s 2021 Taproot upgrade may have increased long-term quantum exposure by making public keys visible on-chain by default, and estimates that about 6.9 million bitcoin are already held in wallets with exposed public keys. Google said it did not publish the attack circuits, instead releasing a zero-knowledge proof using SP1 zkVM and Groth16 so the results could be validated without providing weaponizable details, and said it notified the U.S. government before publication. While the researchers stressed that no cryptographically relevant quantum computer exists today, they argued that the engineering threshold for attacking ECC-based blockchain systems is materially lower than expected and called for migration toward post-quantum cryptography across cryptocurrency ecosystems.
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By 2026-05-12, Ethereum was described as running a coordinated post-quantum initiative through pq.ethereum.org and ongoing interoperability devnets. The effort was presented as a more organized migration response than Bitcoin's fragmented governance around proposals such as BIP-360 and BIP-361.
On 2026-04-08, Blockstream CEO Adam Back said quantum computing is a real long-term theoretical risk to Bitcoin but not an immediate practical threat due to current hardware limits. He urged preparation rather than panic, including giving users a roughly decade-long path to migrate keys to quantum-resistant formats, and said research and experimentation are already underway at Blockstream and on the Liquid network.
On 2026-04-07, Grayscale published a research note urging faster work to make public blockchains quantum-resistant, arguing that Bitcoin’s main obstacle is decentralized governance and consensus rather than technical feasibility. The note highlighted debate over how to handle roughly 6.9 million BTC in wallets with exposed public keys, including whether such coins should be burned, left untouched, or rate-limited.
On 2026-04-04, CoinDesk reported that several Bitcoin quantum-resistance proposals were being advanced or discussed, including BIP 360, post-quantum signature approaches, Tadge Dryja's commit/reveal mempool protection concept, and Hunter Beast's Hourglass V2 for vulnerable legacy addresses. The report said none of these mitigations had been activated yet and noted Bitcoin's decentralized governance could slow deployment of any upgrade.
On 2026-03-31, Google Quantum AI and co-authors published a paper describing five ways a future quantum computer could attack Ethereum, including exposed wallet keys, DeFi and stablecoin admin keys, Layer 2 and bridge cryptography, validator signatures, and Data Availability Sampling ceremony risks. The paper estimated combined Ethereum exposure above $100 billion across major wallets, contracts, L2s, bridges, and staked ETH.
On 2026-03-31, researchers from Caltech and quantum startup Oratomic published a paper arguing that ECC-256 used by Bitcoin and Ethereum wallets could be broken with far fewer quantum resources than many prior estimates. The study said roughly 26,000 qubits could break ECC-256 in about 10 days, and that some wallet protections might be vulnerable with as few as 10,000 physical qubits on a neutral-atom architecture.
The research estimated that about 6.9 million bitcoin are held in wallets with exposed public keys, indicating a larger pool of potentially vulnerable funds than some earlier market estimates suggested. It also warned that real-time attacks on Bitcoin transactions could be plausible within the typical 10-minute confirmation window under ideal assumptions.
Alongside the paper, Google said it did not publish step-by-step attack details to reduce misuse risk. Instead, it released a zero-knowledge proof so others could validate the claims without disclosing weaponizable quantum attack circuits.
On March 31, 2026, Google Quantum AI published a whitepaper estimating that breaking secp256k1 cryptography used by Bitcoin and Ethereum may require fewer than 500,000 physical qubits, far below many prior estimates. The paper described optimized attack methods suggesting a private key could theoretically be recovered in about 9 minutes under idealized conditions.
Before releasing its findings, Google said it conducted responsible disclosure and engaged the U.S. government regarding the research and its implications for cryptocurrency security.
In March 2026, a paper by BTQ Technologies researcher Pierre-Luc Dallaire-Demers and colleagues concluded that using Grover’s algorithm for a quantum 51% attack on Bitcoin mining would require an impractical fleet of roughly 10^23 qubits and about 10^25 watts of power. The study argued that quantum threats to Bitcoin mining are far less realistic than wallet-focused cryptographic attacks.
Bitcoin's Taproot upgrade went live in 2021. Google later assessed that Taproot may have increased future quantum exposure by making public keys visible on-chain by default in more cases.
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New quantum-computing research has significantly reduced the estimated resources needed to break widely used public-key cryptography, increasing pressure on organizations still relying on **RSA-2048** and **256-bit elliptic-curve cryptography**. A 2025 Google Quantum AI preprint reported that RSA-2048 factoring could, in theory, be achieved in less than a week with fewer than **1 million noisy qubits**, down roughly **20×** from earlier estimates, by combining techniques such as approximate residue arithmetic, yoked surface-code storage, and magic state cultivation. Separate reporting also described architectural work that could cut the hardware needed for RSA-2048 attacks by about **tenfold**, reinforcing the trend that algorithmic and engineering advances are shrinking the gap between theory and practical cryptanalytic capability. A 2026 paper on the elliptic-curve discrete logarithm problem similarly reduced the logical-qubit footprint for Shor-based attacks, estimating that a **256-bit prime-field curve** could be targeted with about **1,333 logical qubits**, down from **2,124** in a prior low-width design. Commentary on the new results highlighted an additional Caltech advance in lower-overhead fault tolerance and argued that, taken together, these developments could bring quantum attacks against systems such as **Bitcoin signatures** closer than previously expected, with some estimates dropping from millions of physical qubits to around **25,000** under favorable assumptions. While the work remains theoretical and depends on future fault-tolerant hardware, the direction of travel is clear: advances in quantum algorithms and error correction are accelerating the case for migration to **post-quantum cryptography**.
Jun 29, 2026
The Ethereum Foundation has launched a public post-quantum research hub that consolidates its security research, roadmap, and technical specifications for protecting the blockchain against future quantum-enabled cryptographic breaks. The effort spans Ethereum’s execution, consensus, and data layers and is framed as part of a long-running resilience program, with the Foundation targeting Layer 1 post-quantum protocol upgrades by 2029 while warning that full execution-layer migration will take longer. Ethereum said quantum threats are most likely to become practically relevant in the early-to-mid 2030s, but argued that preparation must begin now because upgrading decentralized infrastructure is a multi-year process. The broader push reflects growing industry coordination on post-quantum cryptography beyond blockchain. Cloudflare and Google are also working on quantum-safe cryptographic improvements for internet infrastructure, underscoring that major platforms are moving from research toward deployment planning. Together, the initiatives show large-scale technology operators preparing for the eventual replacement of current public-key systems before quantum computing can undermine widely used encryption and authentication schemes.
Jun 29, 2026
Quantum computing is rapidly emerging as a transformative technology with the potential to revolutionize various industries, but it also poses significant risks to current cryptographic systems. Bitcoin, which relies on strong cryptographic algorithms such as SHA-256 and the Elliptic Curve Digital Signature Algorithm (ECDSA), faces a unique threat from quantum computers. The security of Bitcoin transactions and wallets is fundamentally based on the computational difficulty of breaking these algorithms, a challenge that quantum computers could potentially overcome. Algorithms like Shor’s algorithm threaten to break ECDSA in a fraction of the time required by classical computers, undermining the security of digital signatures and potentially allowing unauthorized transfers. Similarly, Grover’s algorithm could reduce the difficulty of attacking hash functions, impacting both mining and protocol-level security. The risk is not limited to Bitcoin; quantum computing threatens to break many types of traditional encryption, including both asymmetric and, eventually, symmetric cryptography. Attackers are already harvesting encrypted data today with the intention of decrypting it once quantum capabilities become available, a practice known as 'harvest now, decrypt later.' A common misconception is that the quantum threat is still years away, but recent research and expert opinions suggest that quantum computing could become mainstream within five years or less. This short timeline means that organizations must begin replacing legacy encryption with quantum-resistant solutions now, as the transition is complex and time-consuming. The urgency is heightened by the fact that most businesses are unaware of the full scope of the threat, particularly to symmetric encryption. Security leaders are being urged to prepare for the post-quantum era by assessing their cryptographic assets and developing migration strategies. The ongoing debate and research into quantum resistance are shaping the future of digital security, with the Bitcoin community and broader cybersecurity industry recognizing the need for proactive measures. The continued popularity and financial significance of Bitcoin add to the urgency, as any compromise in its cryptographic integrity could have far-reaching consequences. The challenge is not merely theoretical; it is an immediate concern that requires coordinated action from developers, researchers, and business leaders. The transition to quantum-resistant cryptography is expected to be a major technological undertaking, involving updates to protocols, software, and hardware across the digital ecosystem. As quantum computing advances, the window for effective preparation is closing, making it imperative for organizations to act now to safeguard their data and systems. The future of secure digital transactions, including those on the Bitcoin network, depends on the timely adoption of post-quantum cryptographic standards.
Jun 29, 2026