# What does harvest now, decrypt later mean?

It means an attacker records encrypted traffic today and stores it, to decrypt it once a capable quantum computer exists. Recording is cheap and invisible to you: it can happen at an internet exchange, on a compromised router or at a provider, far from your own network. Only traffic whose key exchange is quantum-vulnerable is at risk, and only data that will still matter when it is decrypted. Health records, designs, source code, long-term contracts, legal files and personal data kept for many years are typical examples; this week's delivery schedule is not. A common way to weigh it is Mosca's inequality: if the years the data must stay secret plus the years your migration takes are more than the years until such a computer arrives, the time to start is now. The practical response is to move the key exchange that protects long-lived data to hybrid post-quantum methods first, because that is where today's recordings would become tomorrow's leaks. Signatures can follow later.

FAQ: [Post-quantum cryptography](https://netsenx.com/en/faq/pqc) · https://netsenx.com/en/faq/what-is-harvest-now-decrypt-later

## Read next

- https://netsenx.com/en/encrypted-traffic-analysis
- https://netsenx.com/en/features
- https://netsenx.com/en/blog/2026-10-27_harvest-now-decrypt-later

## Related questions

- [Which of our data is at risk from harvest now, decrypt later?](https://netsenx.com/en/faq/which-data-is-at-risk-from-harvest-now-decrypt-later)
- [How do I apply Mosca's inequality?](https://netsenx.com/en/faq/how-to-apply-moscas-inequality)
- [Is post-quantum cryptography hype?](https://netsenx.com/en/faq/is-post-quantum-cryptography-hype)
- [Is post-quantum cryptography a board-level topic?](https://netsenx.com/en/faq/is-post-quantum-cryptography-a-board-level-topic)
- [Does the EU require a post-quantum migration plan?](https://netsenx.com/en/faq/does-the-eu-require-a-post-quantum-migration)