[cap-talk] [off-topic] Quantum Encryption Implementation Broken

[David Wagner]

John Carlson  wrote:
>What I've heard is that quantum computation 
>can break any non-quantum encryption.

Nope, that's not believed to be the case.

Quantum computation can break some currently-popular
public-key algorithms (RSA, El Gamal), but there are other
currently-not-popular public-key algorithms that no one knows
how to break with quantum crypto.  Symmetric-key cryptography
is in an even better position; no one knows how to use quantum
cryptography to break, say, AES-256.  (There is a square-root
speedup attack against symmetric-key crypto, but you just double
the key length and that attack becomes irrelevant.)

There are many mistaken impressions surrounding quantum
mechanics, quantum computation, and quantum cryptography.