quantum computing?!? Or, I don't want anyone to read my eMails... never.

Robert J. Hansen cortana at earthlink.net
Thu Jan 2 16:07:02 CET 2003

> curves) I asked myself what those machines can't break (and can be

They can't break the laws of physics.  You're misunderstanding what
superpositional computation (as I prefer to call QC--superpositional
computation is a more accurate term) can and cannot do.

Superpositional computation doesn't allow you to solve any given math
problem.  For some classes of problems it rips through them like a
chainsaw; for other classes of problems it reduces the problem space by
an exponential factor of 0.5; and for other classes of problems it
doesn't help _at all_.  Breaking 256-bit AES by brute force with a
superpositional computer would be as hard as breaking a 128-bit cipher
by brute force today; but using a superpositional computer to add a sum
of numbers would be nonsensical.

> The only thing I can think of which can't be broken by such a machine
> is a one-time-pad vegeniere with: 
>  sizeof(message)==sizeof(key)
>  *and*
>  the key being totaly random

A one-time pad is a Vernam cipher, not a Vigenere.  A Vigenere tableaux
is a primitive polyalphabetic substitution cipher which was successfully
cryptanalyzed by World War One.

Your constraints on the OTP are included in the definition of a OTP. 
OTP/Vernam is a symmetric-key cryptosystem where (a) the keysize equals
the message size and (b) the key values are random with a flat

> It's simple to implement but not to use as you need to transfer large
> keys in a secure way from Alice to Bob... I thought a long time over
> this and I belive I found a solution for the key-exchange-problem. As
> Vegeniere can be implemented cumutative as

Given that you don't know the difference between Vigenere and Vernam,
nor what the limits of superpositional computation are, forgive me for
not going into the many places where you're wrong.  :)  It's enough to
say this is a solved problem.  Look into quantum key exchange.

As a last word, re: your subject.  If you don't want anyone to read your
emails, ever, the only solution is not to send email.  All crypto does,
all crypto can do, is raise the barriers both in time and resources to
read your email.  The barriers can be raised arbitrarily high, but only
finitely; there are no infinite barriers.

More information about the Gnupg-devel mailing list