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Post-quantum

Level: 301 · deep dive

Stub — an outline, not a lesson. There is no runnable example behind this page yet, so nothing on it has been through the check that backs every other claim in this library. The bullets below are the questions the finished page has to answer.

One line: What a quantum computer would actually break, what it would not, and what has already been standardised.

The questions this page has to answer

  • Shor's algorithm breaks RSA and elliptic curves. Grover halves symmetric key strength. Those are different-sized problems — why?
  • So AES-256 is fine and RSA-4096 is not: what does that do to a system's migration plan?
  • ML-KEM and ML-DSA (FIPS 203/204, 2024): what they are based on, and what is already shipping in TLS.
  • Harvest now, decrypt later — which of your data has a secrecy lifetime long enough to care?
  • Why hybrid (classical + PQ together) is the deployed answer rather than a straight swap.

See also