As quantum computing advances, one of the most pressing cybersecurity challenges facing Chief Information Security Officers (CISOs) is the emerging threat known as “harvest now, decrypt later” (HNDL). This threat involves adversaries collecting encrypted data today with the intent to decrypt it in the future once quantum computers become powerful enough to break current cryptographic algorithms.

While full-scale quantum computers capable of this feat are still several years away, the HNDL threat is real today—and proactive CISOs are beginning to take action. Here’s how your organization can prepare.

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What Is “Harvest Now, Decrypt Later”?

In simple terms, HNDL is a long-term cyber-espionage tactic. Threat actors, particularly nation-states, intercept and store encrypted data that they cannot yet break. Their bet? That future quantum computers will eventually allow them to decrypt it—potentially exposing sensitive information, trade secrets, or state intelligence.

This is especially dangerous for data with long-term sensitivity, such as:

• Intellectual property (e.g., pharmaceutical formulas, source code)

• Government and military communications

• Health records

• Financial transactions

• Legal documents

  
  

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Why CISOs Must Act Now

Even though large-scale quantum computers don’t exist yet, data is already being harvested. Once quantum decryption becomes viable, the breach is instantaneous and irreversible.

The National Security Agency (NSA), NIST, and CISA have already issued guidance urging organizations to begin preparing for post-quantum cryptography (PQC)—a new class of cryptographic algorithms resistant to quantum attacks.

Steps CISOs Can Take to Mitigate HNDL Risk

Here are practical strategies to start defending against the HNDL threat now:

1. Inventory and Classify Sensitive Data

Start by understanding what data you have, where it lives, and how long it must remain confidential.

• Identify high-value, long-lived data (e.g., contracts, designs, client records).

• Prioritize data with regulatory or contractual retention requirements.

2. Conduct a Cryptographic Risk Assessment

Review the cryptographic algorithms and protocols in use across your systems.

• Are you using RSA, ECC, or other vulnerable algorithms?

• Are your encryption keys long enough?

• Do you rely on outdated or hardcoded cryptography?

3. Adopt Crypto-Agility as a Core Principle

Crypto-agility is the ability to rapidly swap cryptographic algorithms without overhauling entire systems.

• Design or refactor systems to decouple encryption logic from application logic.

• Invest in cryptographic abstraction layers and flexible key management infrastructure.

4. Begin Migration to Post-Quantum Cryptography

NIST has selected several PQC algorithms for standardization, including:

• CRYSTALS-Kyber (for encryption/key exchange)

• CRYSTALS-Dilithium, FALCON, and SPHINCS+ (for digital signatures)

  
  

Steps to get started:

• Evaluate where PQC can be implemented today (e.g., internal tools, test environments).

• Work with vendors to understand their PQC roadmaps.

• Stay aligned with NIST’s timeline for final standards (expected by 2024–2025).

5. Secure the Supply Chain

Ensure your third-party vendors and partners are also preparing for PQC.

• Include post-quantum readiness in vendor risk assessments and contracts.

• Share expectations and timelines for PQC migration.

6. Implement Strong Network and Data Controls

Even if quantum-safe encryption isn’t yet deployed, preventing data interception now reduces HNDL risk.

• Enforce strict TLS configurations (e.g., TLS 1.3 with perfect forward secrecy).

• Use strong VPNs and limit access to sensitive data.

• Consider quantum-safe key exchange for highly sensitive communications.

7. Monitor the Quantum Threat Landscape

Stay informed about quantum research, standardization efforts, and nation-state activity.

• Engage with CISA, NIST, and industry consortia (like the Quantum Economic Development Consortium).

• Evaluate threat intelligence for early signs of quantum capability development.

  
  

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Conclusion: Prepare Today for Tomorrow’s Threat

The “harvest now, decrypt later” threat may seem distant—but it’s already in motion. CISOs who start planning today will not only protect their organization’s future but will also improve agility, compliance, and trust in the present.

By adopting crypto-agility, investing in post-quantum readiness, and securing long-lived data, CISOs can ensure their organization is not caught off-guard when the quantum moment arrives.

Proactive security isn’t just about today’s threats—it’s about anticipating tomorrow’s. The quantum era is coming. The question is: will your data be ready?