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Quantum Sundays |71⟩ Harvest Now, Decrypt Later: A Guide to Post-Quantum Cryptographic Migration
How Organizations Can Defend Against Quantum-Era “Harvest Now, Decrypt Later” Attacks with Post-Quantum Cryptography, Hybrid TLS, and Crypto-Agile Migration
tl;dr — Harvest Now, Decrypt Later is the strategy of collecting encrypted data today and decrypting it years from now, once a cryptographically relevant quantum computer can break the public-key cryptography that protects nearly every secure connection. The risk does not start when that machine arrives. It starts the moment your ciphertext is captured, because any secret that must outlive your migration window is already exposed. Forward secrecy does not save you, larger keys do not save you, and the only real defense is moving key establishment to post-quantum or hybrid cryptography before the harvesting window closes. This piece covers the full picture: the mechanism, Mosca’s risk math, the attack taxonomy, working code, the documented collection infrastructure, the standards and deadlines now in force, and where your sector sits on the exposure curve.
Harvest Now, Decrypt Later (HNDL) is the strategy of collecting encrypted data today and…