Quantum Estimates Are Shrinking Faster Than Your Migration Plan

This case study examines the technical challenge of decreasing resources needed to break RSA-2048 encryption and its implications for your risk management strategy.

The Challenge

Alice & Bob, a quantum computing company, estimates that RSA-2048 can be factored using fewer than 23,000 physical qubits in as little as three days. This is significantly fewer than Google Quantum AI's 2025 estimate of 1 million qubits.

The trend is clear: estimates for the resources needed to break RSA-2048 are dropping rapidly. In 2019, it was estimated to require 20 million noisy physical qubits. By 2025, this dropped to under a million. Alice & Bob's cat qubit requirement has fallen from 350,000 in 2023 to 23,000 now.

For your team, the challenge isn't predicting a "Q-Day." It's recognizing that your cryptographic risk assessment may already be outdated.

Environment and Constraints

Several factors influence your decision-making.

Unproven Hardware Estimates. Alice & Bob's estimates are based on assumptions about cat qubits that need validation. These qubits are assumed to have fewer errors than current technology. Whether they perform as expected in real-world conditions is still unknown.

Varied Data Lifetimes. The time it takes to break a key may not matter for short-lived data but is critical for long-term confidentiality needs, like medical records or state secrets.

Slow Migration. The pace of technological change is outstripping the speed at which organizations are updating their cryptographic systems. Companies like Google and Oratomic are pushing the pace, but migration remains slow.

The Approach: What You Should Do

Adapting to Cat Qubits. The reduction in qubit requirements stems from engineering improvements, not new physics. Treat the timeline as a moving target.

Harvest Now, Decrypt Later. This threat model makes quantum risk a current compliance issue. Data stolen today can be decrypted later. Assess whether your data's confidentiality needs outlast the point when RSA-2048 becomes vulnerable.

A practical approach for your team:

1. Build a Cryptographic Inventory. ISO/IEC 27001:2022, Annex A control 8.24 requires defined cryptographic rules. You need to know what algorithms you're using to write these rules. Identify where RSA and elliptic-curve cryptography are used.
2. Classify by Confidentiality Lifetime. Pair your information classification scheme with a retention horizon. Prioritize data needing long-term confidentiality.
3. Run a Scenario-Based Risk Assessment. Include a quantum-capable adversary scenario in your risk assessment under clause 6.1.2. Focus on reasoning, not false precision.
4. Document a Risk Treatment Plan. Under clause 6.1.3, assign responsibilities for migrating critical data to quantum-safe cryptography.
5. Engage with Suppliers. Your risk includes third-party data handlers. Integrate cryptographic expectations into supplier reviews, as per Annex A 5.19 and 5.20.

For SOC 2, this work supports your risk assessment under CC3.2 and encryption commitments under the Confidentiality criteria.

Results and Metrics

This is a threat assessment, not a completed migration. Key findings include:

• Resource estimates for RSA-2048 have drastically decreased from 20 million qubits in 2019 to under a million by 2025.
• Alice & Bob's estimates fell from 350,000 qubits in 2023 to 23,000 now.
• For elliptic-curve cryptography, 30,000 qubits could break it in about an hour.
• Dormant Bitcoin in older addresses remains vulnerable to such attacks.

Doug Finke of Global Quantum Intelligence advises starting quantum-safe remediation programs immediately.

What You'd Do Differently

If your last cryptography review treated quantum risk as a "monitor annually" item, adjust your approach:

• Trigger Reviews on Estimate Changes. A drop in qubit requirements should trigger a risk assessment review. Define this as a trigger in your ISMS monitoring approach. ISO/IEC 27004
• Start Inventory Work Now. Don't wait for peer review to begin inventory and classification. These steps are cost-effective and beneficial regardless of whose estimates are correct.

Takeaways for Your Team

• The trend across estimates is consistent, even if individual figures vary.
• "Harvest now, decrypt later" turns a future capability into a current risk.
• Start with inventory and data-lifetime classification; everything else depends on them.
• Record the quantum scenario in your risk assessment and Risk Treatment Plan for audit transparency.
• Treat supplier cryptography as part of your own exposure.

You don't need to believe the three-day figure to act. You only need to recognize that the number is decreasing and your migration timeline likely hasn't kept pace.