quantum hype

[Arnold G. Reinhold]

At 10:18 PM +0000 9/13/03, David Wagner wrote:
>...
>One could reasonably ask how often it is in practice that we have a
>physical channel whose authenticity we trust, but where eavesdropping
>is a threat.  I don't know.

I think there is another problem with quantum cryptography. Putting 
aside the question of the physical channel, there is the black box at 
either end that does all this magical quantum stuff. One has to trust 
that black box.

- Its design has to thoroughly audited  and the integrity of each unit verified

- It has to be shipped securely from some factory or depot to each end point

- It has to be continuously protected from tampering.

It seems to me one could just as well ship a 160 GB hard drive filled 
with random keying material to each endpoint. The disk drive would 
receive the same  level of physical security as the quantum black 
boxes. At one AES256 key per second, a 160GB hard drive holds 150 
years of keying material.  For forward security one can erase used 
keys.  (If you don't trust disk erasing, ship a carton of CD-Rs or 
DVD-Rs and burn them as they are used up).

The 160 GB hard drive has a couple of advantages over quantum key exchange:

- No special assumptions about the channel are needed. One can use 
the existing  Internet, telephone, satellite and even shortwave 
infrastructure.

- The hard drives and the PCs to use with them can be purchased off 
the shelf from a random computer store. No one is alerted that you 
are engaging in secret communications so  no one is likely to tamper 
with your equipment before you get it.

- The necessary software is easy to write and audit

- I expect a quantum crypto box to cost far more than a160 GB disk 
drive, not to mention the cost of the dedicated fiber channel.

What am I missing?


Arnold Reinhold

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