On 6/29/2020 6:57 PM, Punk-Stasi 2.0 wrote:
On Sun, 28 Jun 2020 23:54:43 +0000 (UTC)
jim bell <jdb10...@yahoo.com> wrote:
Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography.
https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography
bullshit as usual.
As far as I know so called 'quantum key distribution' needs an
authenticated 'classical channel' to work, so it's completely pointless.
There seem to be two kinds of Quantum Crypto out there
- the kind that needs a piece of fiber
- the kind that lets you send your photons in free space between ground
and satellite.
The former's a very niche application, and doesn't protect you about
things like pseudonymity vs contact tracing (because you follow the
piece of fiber and see who's at the other end, or follow the money and
see who's renting the fiber :-).
It's more useful if your threat model is "Auditors" than "Spies";
otherwise you can send an extra diverse dude with a briefcase handcuffed
to their arm for an initial authentication key exchange and then use
another layer of Diffie-Hellman for authentication, maybe with an
annoyingly long ECC key, while also printing the authentication public
key in a classified ad in the NY Times or Pravda or Federal Register.
The latter's "interesting"; I'm skeptical about its usefulness, but
haven't looked into it deeply, beyond a quick read of
https://arxiv.org/ftp/arxiv/papers/1909/1909.13061.pdf
There seem to be three approaches
- one end-to-end quantum-protected hop (ground to bird to ground)
- two (ground to bird-in-the-middle, bird-in-the-middle to ground)
- two (trusted-bird sends entangled pair, one to Alice, one to Bob)
Approach 1 doesn't appear to exist, approach 2 lets you use two
prepare-and-measure channels (meh), approach three could be useful-ish
Also, my current guess/understanding is that there isn't any 'entanglement' at all.The "trusted-bird sends entangled pair, one to Alice, one to Bob" method
uses entanglement, but needs a bigger satellite than the
bird-in-the-middle approach. (According to the paper, it needs more
than a 100kg satellite, as opposed to a single-end thing which can fit
on an under-10kg cubesat.)
