Quantum direct communication: secrecy without key distribution

Eugen Leitl eugen at leitl.org
Fri Dec 5 08:16:09 EST 2008

From: the physics arXiv blog <howdy at arxivblog.com>
Subject: the physics arXiv blog
To: eugen at leitl.org
Date: Fri, 05 Dec 2008 13:10:50 +0000

[1]the physics arXiv blog

   [2]Quantum direct communication: secrecy without key distribution

   Posted: 04 Dec 2008 09:13 PM PST


   An interesting development in the world of quantum encryption.

   In the last couple of years, we've seen a number of quantum key
   distribution systems being set up that boast close-to-perfect security
   ([4]although they're not as secure as the marketing might imply).

   These systems rely on two-part security. The first is the quantum part
   which reveals whether a message has been intercepted or not. Obviously
   this is no use when it comes to sending secret message because it can
   only uncover eavesdroppers after the fact.

   So Alice sends a one time pad over this quantum channel that she and
   Bob can later use to encrypt and send a message classically. If this
   key is compromised, Alice sends another.

   What guarantees the security is not quantum mechanics but the second
   part of the system: the one time pad.

   Today, Seth Lloyd and colleagues at the Massachusetts Institute of
   Technology in Cambridge, publish a way of guaranteeing security over a
   quantum channel without having to fall back on a one time pad.

   Their idea is to send a message over a standard quantum channel
   without bothering with a one time pad. The security, they say, can be
   monitored by randomly checking the channel to see whether any of the
   qubits are being lost (potentially to Eve).

   The security of the channel then depends on how much loss of
   information Alice and Bob are willing to accept, but can always be
   improved by checking more often for eavesdroppers.

   Quantum direct communication, as the team call it, looks interesting.
   But it will be demanding to implement, not least because any noise in
   the channel will look like an eavesdropper. So it looks as if this
   idea will have to be limited to short range applications where noise
   can be kept to a minimum.

   Nevertheless, a cool idea.

   Ref: [5]arxiv.org/abs/0802.0656: Quantum Direct Communication with
   Continuous Variables

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Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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