A concerning threat looms on the horizon: “Harvest Now, Decrypt Later” (HNDL) attacks, also known as “Store Now, Decrypt Later” (SNDL) attacks. These sophisticated operations leverage a deceptively simple premise: adversaries collect encrypted data today with the intention of decrypting it once quantum computing capabilities mature enough to break current encryption methods.
Understanding the Threat Model
HNDL/SNDL attacks operate on a delayed gratification principle. Attackers intercept and store encrypted communications and data that remain secure under today’s cryptographic standards. However, they’re betting on future quantum computing advancements to retroactively decrypt this information. This strategy is particularly concerning for data with long-term value — financial records, intellectual property, state secrets, or personal information that remains sensitive for decades.
The primary catalyst for this threat is the development of quantum computers capable of running Shor’s algorithm efficiently. This algorithm can factor large prime numbers exponentially faster than classical computers, potentially undermining RSA and other public key cryptographic systems that form the backbone of modern secure communications.
Why Organizations Should Be Concerned Today
The window of vulnerability is already open. Sensitive data encrypted today could be compromised when quantum computers reach sufficient power. For information that needs to remain confidential for extended periods, this represents an immediate risk.
More concerning is that these attacks are already happening. Nation-states and sophisticated threat actors are likely harvesting and storing encrypted data now, anticipating future decryption capabilities. As former NSA Director Admiral Mike Rogers noted, “Data that needs to be protected for decades needs protection from quantum computers today.”
Mitigation Strategies
Organizations should begin planning to implement quantum-resistant security measures now:
Post-Quantum Cryptography (PQC): Transition to cryptographic algorithms designed to resist quantum attacks. The National Institute of Standards and Technology (NIST) released the first set of quantum-safe encryption algorithms and there are more forthcoming.
Crypto Agility: Build systems that can quickly transition between cryptographic algorithms as security requirements evolve.
Hybrid Approaches: Implement both classical and post-quantum cryptographic methods simultaneously during the transition period.
The Road Ahead
Organizations must balance immediate security needs with preparation for the quantum future. As we enter this new era of cryptographic uncertainty, security frameworks must evolve to address not just present threats but also the looming capabilities of future adversaries. The time to prepare for quantum-resistant cryptography isn’t when quantum computers break existing systems—it’s now, before the harvested or stored data becomes a vulnerability.
For organizations handling sensitive data, understanding and mitigating HNDL/SNDL threats should be an essential part of contemporary security planning. Quantum Xchange is here to help. Contact one of our experts to find more about how we can protect against HNDL/SNDL attacks.
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