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Harvest Now, Decrypt Later: Quantum Security Risk. (2026).

Harvest Now, Decrypt Later: Quantum Security Risk

The Palo Alto Networks source describes HNDL as a present-day threat: attackers can collect or steal encrypted data now and store it until future quantum computers may be able to decrypt it. In other words, the risk starts when the data is intercepted or copied, not when quantum computers finally arrive.[1][2]

This makes HNDL especially relevant for data that must remain confidential for a long time, because the value of the stolen ciphertext can persist for years or decades before a decryption attempt is possible.[3]

What is at risk and how to respond

  • The main cryptographic concern is public-key cryptography, especially RSA and elliptic-curve cryptography, which the source says are expected to be vulnerable to sufficiently powerful quantum computers.[4]
  • The most exposed data is long-lived sensitive information, including government records, financial data, healthcare information, intellectual property, and defense data.[5]
  • The source recommends starting post-quantum migration now by building cryptographic inventories, improving crypto-agility, checking vendor readiness, and creating migration roadmaps.[6]

HNDL is difficult to detect and reverse because once encrypted data has been collected, organizations cannot easily "unharvest" it; they can only reduce future exposure by migrating systems and data protection strategies before quantum decryption becomes practical.[7][8]