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Security Fundamentals & Crypto · Advanced

Harvest Now, Decrypt Later (HNDL)

Strategy of collecting encrypted data today to decrypt it once a quantum computer can break the encryption.

Definition

Also called store now, decrypt later, HNDL threatens data with long confidentiality requirements, such as government secrets, health records, and intellectual property. It makes key exchange the most urgent PQC migration target. Hybrid ML-KEM key exchange in TLS and SSH mitigates it.

Example

A nation-state records VPN traffic from a defense contractor to decrypt in 15 years.

Exam tip

HNDL is why key establishment is migrated to PQC before signatures.

Related terms