[ExI] 10 Breakthrough Technologies 2017

[John Clark]

On Mon, Feb 27, 2017 at 12:00 PM, Brent Allsop <brent.allsop at gmail.com>
wrote:

​>​
> I know next to nothing about quantum computers.  All I know is that some
> people claim they will be able to render crypto currency security no longer
> secure.  What would you guys give the odds that something like quantum
> computers could sometimes make crypto currencies not work.
>

​
Although useful for certain types of problems I doubt a D-wave type quantum
machine would be much good at breaking codes because no matter how big you
make it the thing is not Turing Complete and so it's not a true general
purpose computer. But the machines Google, IBM and Microsoft are trying to
build would be Turing Complete, so if they're successful then Bitcoin is
​
dead
​,​

​and so​
is
​
RSA Diffie-Hellman
​,​
Elliptic curve, and all currently used forms of
​
public key cryptography.

There still might be some hope if Lattice-based cryptography
​
could be improved
​,​
but right now keys they must use are impractically large. And there are
more fundamental problems, although the very hardest lattice problems would
probably be difficult even for a Quantum Computer to solve the average
problem would not be. As a analogy not every super large number is
difficult to factor (2^64 is remarkably easy) only some super large number
are hard. RSA can find those hard to factor numbers simply by multiplying 2
prime numbers together, but nobody has yet found a easy way to pick out the
few super hard lattice problems from the far more numerous easier ones. A
similar flaw doomed knapsack
​
encryption 20 years ago, before that people thought it would be a serious
competitor to RSA.

However if a Turing complete Quantum Computer is built the effect it will
have on cryptography will be trivial compared to other changes it will
bring to society.


> ​> ​
> even a quantum computer could never solve a 10K byte key right?
>

​Maybe, but I wouldn't bet on it. I would need to think long and hard
before I would dare say that even the best Quantum Computer could never
solve X. About 10 years ago somebody calculated it would take the best
supercomputer of the day 24 billion years to calculate the energy levels in
ferredoxin
​, a protein ​used in photosynthesis. Microsoft says if their Quantum
Computer works as they hope it should be able to do it in about an hour.
Forget cryptography, the ability to do chemistry without test tubes is what
will turn the world upside down.

​ ​
John K Clark
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