Quantum risk management addresses the threat that future quantum computers pose to current cryptographic systems. Unlike traditional cybersecurity risks, quantum risk has a unique characteristic: adversaries can capture encrypted data today and decrypt it years later when quantum computers become available.
This guide provides a framework for understanding, assessing, and mitigating quantum risk across your organization. We'll cover the Mosca inequality for timeline analysis, threat categorization, risk quantification methods, and practical mitigation strategies.
Understanding Quantum Risk
Quantum risk differs from conventional security risks in several important ways:
- Temporal displacement: The attack vector exists today (data capture), but the exploit occurs in the future (quantum decryption)
- Certainty of capability: Quantum computers will eventually break current cryptography - only the timeline is uncertain
- Irreversibility: Data captured today cannot be "uncaptured" once quantum computers arrive
- Asymmetric impact: Data with long confidentiality requirements faces higher risk than transient data
The HNDL Threat
Harvest Now, Decrypt Later (HNDL) is the primary quantum threat facing organizations today. Adversaries capture encrypted network traffic and store it for future decryption when quantum computers become available.
The Mosca Inequality
The Mosca Inequality provides a framework for determining when to begin quantum migration:
If X + Y > Z, your data is at risk. The sum of how long data must remain confidential (X) and how long migration will take (Y) exceeds the time until quantum computers arrive (Z).
Timeline Analysis Example
Quantum Risk Timeline
| Scenario | X (Shelf Life) | Y (Migration) | Z (Quantum Threat) | Risk Status |
|---|---|---|---|---|
| Healthcare records (HIPAA) | 50+ years | 5 years | ~10 years | Critical Risk |
| Financial trading data | 7 years | 3 years | ~10 years | Moderate Risk |
| Session tokens | Hours | 2 years | ~10 years | Lower Risk |
Threat Categories
Quantum threats can be categorized by their timing and impact:
HNDL Attacks
Data captured today, decrypted in the future. Active threat against internet-exposed encrypted communications. Highest priority for long-lived confidential data.
Key Compromise
Long-term secrets (root CAs, master keys) captured via HNDL. Once compromised, enables decryption of all protected data and signing of malicious content.
Signature Forgery
Digital signatures become forgeable once private keys are exposed. Affects code signing, document authentication, and identity verification.
Authentication Bypass
Breaking authentication mechanisms that rely on public-key cryptography. Enables identity impersonation and unauthorized access.
Risk Assessment Framework
Assess quantum risk across two dimensions: impact severity and exposure likelihood.
Impact Severity
- Critical: Compromise of long-lived secrets, classified data, critical infrastructure
- High: Sensitive PII, financial records, intellectual property
- Medium: Internal communications, operational data
- Low: Public information, transient session data
Exposure Likelihood
- High: Internet-facing, high-value target, nation-state interest
- Medium: Limited external exposure, moderate value
- Low: Air-gapped, minimal external connections
Risk Matrix
Building a Quantum Risk Register
Document quantum risks in a structured register for tracking and prioritization:
Mitigation Strategies
Address quantum risk through layered mitigation strategies:
Immediate Actions
- Build cryptographic inventory: Document all quantum-vulnerable cryptography
- Classify data by shelf life: Identify data requiring long-term confidentiality
- Enable hybrid TLS: Deploy hybrid key exchange on internet-facing services
- Prioritize high-risk systems: Focus on PKI, key management, classified systems
Medium-Term Actions
- Migrate to PQC: Implement ML-KEM for key exchange, ML-DSA for signatures
- Update PKI: Deploy hybrid or pure PQC certificate chains
- Re-encrypt archives: Protect stored data with quantum-safe encryption
- Vendor coordination: Ensure third parties support PQC
Ongoing Actions
- Monitor threat landscape: Track quantum computing advancement
- Maintain crypto agility: Ensure ability to update algorithms rapidly
- Regular assessment: Re-evaluate risk as timelines evolve
- Incident response: Plan for potential quantum-related breaches
Communicating Risk to Leadership
Executives and board members need quantum risk communicated in business terms:
| Technical Concept | Executive Translation |
|---|---|
| HNDL attack | Data stolen today can be read when quantum computers arrive |
| Mosca inequality X+Y>Z | If migration takes longer than we have, we're already too late |
| Cryptographic agility | Ability to swap security algorithms without major disruption |
| Hybrid cryptography | Belt-and-suspenders approach using both old and new security |
| PQC migration | Upgrading security infrastructure to resist quantum attacks |
Frequently Asked Questions
Next Steps
Begin managing quantum risk in your organization:
- Take the assessment - Use our QRAMM Assessment to evaluate your current state
- Build your inventory - Follow the Cryptographic Inventory Guide
- Apply Mosca analysis - Calculate X+Y>Z for your critical data categories
- Create risk register - Document and prioritize quantum risks
- Brief leadership - Share the Executive Brief with decision-makers