[cryptography] abstract: Air to Ground Quantum Key Distribution

D. J. Bernstein djb at cr.yp.to
Thu Sep 20 16:39:57 PDT 2012

Zack Weinberg writes:
> I've seen claims that quantum key agreement lets both parties detect a
> man in the middle with no prior communication and no trusted third party.

Nope. The security of QKE relies on the parties both knowing a shared
secret key to authenticate messages. This begs the questions of

   (1) how the parties communicated this secret---this doesn't have to
       be a _prior_ secure channel but it does have to be a separate
       secure channel;

   (2) why the parties are bothering to use QKE to generate randomness
       when they can much more cheaply generate local randomness and
       send it through the separate secure channel; and

   (3) why the parties are bothering to generate so much randomness in
       the first place when they can much more cheaply use the key as an
       AES key to encrypt and authenticate messages.

See http://cr.yp.to/talks/2009.10.06/slides2.pdf for a more detailed
cost-benefit analysis.

---D. J. Bernstein
   Research Professor, Computer Science, University of Illinois at Chicago
cryptography mailing list
cryptography at randombit.net

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