06 · The system

The threat

Shor eats RSA and Diffie–Hellman. Grover nicks AES and hashes — double the key. Lattices are the migration. Store now, decrypt later is why this is not a 2040 problem.

In English

Shor kills the public-key stories that are hidden periods (RSA, Diffie–Hellman, elliptic curves). Grover is only a square-root speedup, so we double AES keys and maybe lengthen hashes. New lattices are the migration. Ciphertext saved today can wait for a future machine — that is the urgency.

Try this: Click each layer. Read slogan vs actual. “Quantum breaks encryption” is the slogan. The rest is the actual.
Keep this: Shor eats public-key periods. Grover nicks symmetric. Lattices stand. Harvest-now is why it matters now.

Lab · what actually dies

Shor eats this

RSA

Security is “factoring n is hard.” Period-finding on aˣ mod n, then a classical gcd, gives the factors. The quantum piece is Volume III’s QFT, at a size no fridge has.

The slogan: 2048-bit n, and a belief about factoring.
The actual: A large, clean quantum computer. Not a NISQ chip. Then the modulus is public wastepaper.

Shor is exponential against hidden-period problems: factoring, discrete log, elliptic curves. Grover is quadratic against unstructured search: keys, preimages. Different verbs.

The operational sentence is harvest-now-decrypt-later. Ciphertext you ship today is a gift to whoever first runs a large QFT. Symmetric traffic with a doubled key is not.