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@randombit.net http://lists.randombit.net/mailman/listinfo/cryptography ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE