Re: Crypto and new computing strategies

[fnerd@smds.com (FutureNerd Steve Witham)]

> Jim Choate writes:
> 
> > In the latest issue of Scientific American there is an article...

On Seth Lloyd's grain-of-salt computer, actually.  I didn't know he was
going to build one.  Anyway, his technique *may* be useful to make quantum
computers, but it's more likely to be useful for making regular 
deterministic massive single-instruction-multiple-data computers out of 
fairly simple crystals--"maybe even a grain of salt."

His technique would make every repeating unit of the 3D crystal into a
computing unit.  You lose a couple factors of 10 for addressing,
making higher-level modules, and error-correction.  Still, that's a lot
of compute power.

Tim May says-

> No need to worry just yet.
> 
> There is no convincing evidence that "quantum computers" can calculate
> in any way differently from "ordinary" computers.

Right.  This is just a large power increase using deterministic stuff.
It's based on electrons in the shells of atoms in crystals responding
to different frequencies of photons depending on their own and 
neighboring atoms' shells' states.

> Devices that are built on a size scale where quantum effects are
> important, such as quantum-well devices, don't use QM as a
> computational mechanism per se. The devices are just real small. But
> not small enough to matter for large RSA moduli--the computations
> required to factor a 1000-decimal-digit number swamp even a universe
> _made_ of computers!

Which is what a naive guess would have said about 129-digit numbers.
I would love to see some sort of curve of factoring algorithm
efficiencies over time.  You could show the log of the difficulty for
a selection of number sizes over the past hundred years, say.  The 
experts say it's flattening out and will probably stay that way.

A sudden jump in the high end of computer power would mean that we
would need to use larger keys sooner than we thought.  A key length
requiring a little bit more work on the user's part means a 
lot more work on the cracker's part, but I don't know how many more
bits of key compensate for a 10^9 increase in cracking power, say.

-fnerd
quote me

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