Harvest Now, Decrypt Later

"Harvest now, decrypt later" (HNDL) describes an attack strategy where an adversary captures and stores encrypted traffic or data today, without being able to decrypt it yet, betting that a sufficiently powerful quantum computer will exist within the data's required confidentiality lifetime.

Why it's the central argument for urgency

Unlike most cybersecurity threats, HNDL doesn't require the attack capability to exist yet. It only requires the recording capability, which already exists at scale for any adversary capable of passive network interception or data exfiltration. The risk calculation is:

Risk = data is still sensitive when quantum decryption becomes feasible

This reframes PQC migration urgency around data retention requirements, not around when quantum computers will arrive. A password reset token that expires in ten minutes has effectively zero HNDL exposure. A state secret, a genomic record, or a long-term intellectual property filing with multi-decade confidentiality requirements has significant exposure even if a cryptographically relevant quantum computer is a decade or more away.

Who faces the highest exposure

• Government and defense, for classified material with multi-decade classification periods.
• Healthcare and genomics, where patient data confidentiality requirements can span a lifetime.
• Financial services, for records with long regulatory retention and fraud-relevant windows.
• Intellectual property and legal, for patents, trade secrets, and litigation material with long relevance windows.

How it shapes migration prioritization

Every major PQC migration framework (NIST, NSM-10, NCSC, ENISA) recommends prioritizing migration based on data sensitivity lifetime rather than migrating systems in an arbitrary or purely technical order. A system protecting data that must remain confidential past the point a quantum computer is expected to exist is a near-term migration priority regardless of how technically difficult that system is to migrate.