Swiss on a Roll With Quantum Crypto

[Dave Farber <dave () farber net>]

___

Dave Farber  +1 412 726 9889



...... Forwarded Message .......
From: Johan Ovlinger <johan () ccs neu edu>
To: dave () farber net
Cc: Ip <ip () v2 listbox com>
Date: Thu, 30 Sep 2004 17:17:28 -0400
Subj: Re: [IP] Swiss on a Roll With Quantum Crypto

David Farber wrote:
> I suggest that a more accurate statement would be, "It is the only
> solution offering long term confidentiality and which cannot be
> compromised by *CURRENTLY KNOWN* scientific or technological
> advances".
>
> I, for one, don't know where, or when, the next Einstein, or
> Feynman, or Hawking will arrive on the scene.  I certainly don't
> know what they will tease out of nature's secret treasure trove.

Dave, Bob, IPers,

as I understand these things (interested layman, at most), quantum 
cryptography doesn't actually encrypt anything. Rather, it allows you 
to detect whether a message has been intercepted (copied) en-route.

 From this, it is fairly easy to build a secure encryption system that 
functions over conventional channels. (Don't send the message over the 
safe channel, but rather send a one-time-pad, and only use pads not 
intercepted.)

The main strength of QC is that while it may possibly be invalidated 
by future breakthroughs, these breakthroughs would still not allow the 
attacker access to old communications, as without these breakthroughs, 
no copies of the old messages could have been made.

Ultimately, this may be a moot breakthrough: as Bruce Schneier points 
out, it is rarely -- if ever -- that the cryptosystem is the weak 
point in a security breach.  Humans and processes are much easier to 
break than the crypto itself.  People spend millions on security 
devices and then leave the password on a post-it note, or don't notice 
the key-logger secretly attached to their keyboard's usb cable.

Lastly, although the article doesn't go into specifics, unless they 
are happy with transmission rates of ~ 100kbs (I seem to recall a 
recent speed record in quantum bit generation around that figure), 
they'll need to just use QC for key exchange and resort to 
conventional encryption for the bulk of the message itself. In this 
case, future breakthroughs in cryptography could very well compromise 
old transmitted messages, by merely attacking the conventional crypto- 
system.





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