Main Points:
- Google’s recent research shows that cracking 2048-bit RSA encryption may require fewer than one million noisy qubits, reducing previous estimates by a factor of twenty.
- Innovations in approximate modular arithmetic and magic-state distillation drive this efficiency gain.
- Today’s leading quantum processors, including Google’s Willow (105 qubits) and IBM’s Condor (1,121 qubits), remain far from the scale needed for practical attacks.
- Bitcoin’s elliptic-curve cryptography (Secp256k1) faces similar quantum threats, albeit requiring different qubit resources.
- Asset managers such as BlackRock have flagged quantum risk in official Bitcoin ETF filings.
- NIST recommends sunsetting vulnerable systems by 2030 and banning use by 2035, while collaborating on post-quantum cryptography standards.
- Bitcoin developers have proposed wallet-migration schemes to preempt future quantum attacks.
Introduction
Quantum computers exploit superposition and entanglement to solve certain mathematical problems exponentially faster than classical machines. Since Shor’s landmark 1994 algorithm demonstrated that quantum devices could, in principle, factor large integers in polynomial time, the countdown on conventional encryption systems has begun. In late May 2025, Google Quantum AI researchers announced a monumental reduction in the estimated number of qubits needed to crack widely used RSA-2048 keys, signaling that the quantum threat to digital assets—including Bitcoin—may arrive sooner than previously imagined.
Google’s Quantum Leap: Breaking RSA with Fewer Qubits
On May 21, 2025, Craig Gidney and colleagues at Google published a preprint showing that an RSA-2048 integer could be factored in under one week on a quantum computer with fewer than one million noisy physical qubits, a twentyfold improvement over their own 2019 estimate of twenty million qubits. This finding recalibrates threat models for all systems that rely on RSA, from secure websites to encrypted email and financial transactions.
Technical Innovations: Algorithms and Error Correction
Two breakthroughs underpin Google’s qubit reduction:
- Approximate Modular Arithmetic: By adopting approximate residue techniques, Google doubled the throughput of modular exponentiation, the computational core of integer factoring.
- Enhanced Error Correction: Improvements in magic-state distillation and surface-code encoding tripled logical-qubit density, meaning fewer physical qubits per logical qubit.
Together, these gains slash the overhead traditionally needed for fault tolerance in large-scale quantum algorithms.
Current Quantum Hardware Landscape
Despite theoretical progress, practical hardware remains orders of magnitude below attack scale. Google’s Willow processor, unveiled in December 2024, comprises 105 superconducting qubits and demonstrates below-threshold error correction only at small scales. IBM’s Condor machine, at 1,121 qubits, similarly cannot yet sustain the coherence or connectivity needed for Shor’s algorithm on large integers. Consequently, realistic quantum attacks on RSA or elliptic-curve systems remain at least a decade away, according to leading experts.
Implications for Bitcoin’s Elliptic-Curve Cryptography
Bitcoin secures transactions using the Secp256k1 elliptic-curve Digital Signature Algorithm (ECDSA), which relies on the discrete-logarithm problem. Quantum computers running Shor’s algorithm can solve discrete logs with resource requirements comparable to factoring RSA keys of similar strength. Early estimates placed the qubit count for attacking 256-bit ECDSA keys at around one-third of that for RSA-2048; Google’s new methods may reduce that further, heightening the long-term risk to Bitcoin addresses and wallets. However, even with improved algorithms, bridging from a million qubits for RSA to the tens of thousands needed for ECC attacks remains a formidable hardware challenge in the near term.
Industry Response: BlackRock and Asset Managers Brace
Recognizing the quantum risk, BlackRock filed an amendment to its Bitcoin ETF documents on May 9, 2025, explicitly warning that advances in quantum computing could compromise Bitcoin’s cryptography and expose investors to theft. Other institutional asset managers are evaluating insurance products, operational risk frameworks, and potential migration to quantum-resistant blockchains to safeguard holdings.
Standardization Efforts: NIST and Post-Quantum Cryptography
The U.S. National Institute of Standards and Technology (NIST) recommends phasing out vulnerable public-key algorithms by 2030 and prohibits their use after 2035. NIST has already standardized several post-quantum cryptographic (PQC) algorithms—including CRYSTALS-Kyber for key exchange and CRYSTALS-Dilithium for signatures—as interim defenses. Google and other industry leaders are collaborating with NIST to integrate PQC into existing protocols, from TLS for web traffic to blockchain consensus mechanisms.
Community Action: Bitcoin Developer Proposals
In April 2025, Bitcoin core developers initiated discussions on forced key rotation: mandating that funds held in addresses older than a certain block height be moved to newly generated quantum-resistant addresses. Although controversial—given potential privacy and user-experience drawbacks—this proposal underscores the urgency of preparing for a post-quantum world. Parallel efforts explore layer-two solutions that incorporate PQC signature schemes without altering Bitcoin’s base protocol.
Looking Ahead: Timeline and Future Outlook
While today’s quantum machines are far from the scale needed to threaten real-world RSA or ECC keys, the exponential pace of development demands vigilance. If hardware improvements follow past trends, the community could see million-qubit processors by the early 2030s. Organizations should:
- Monitor quantum hardware roadmaps from Google, IBM, IonQ, and emerging photonic platforms.
- Invest in PQC pilots to validate performance and integration with blockchain nodes.
- Engage with standards bodies to shape adoption timelines for quantum-safe protocols.
By coordinating research, standardization, and community governance, stakeholders can navigate the quantum transition proactively rather than reactively.
Conclusion
Google’s groundbreaking reduction in the qubit count required to factor RSA-2048 highlights the accelerating quantum threat to modern cryptography, including Bitcoin’s elliptic-curve security. Although practical attacks remain years—if not decades—away, asset managers, standards organizations, and the crypto community must act now to develop, standardize, and deploy post-quantum defenses. Through collaboration and foresight, the industry can safeguard digital assets against the coming quantum era.
