Cryptography-Digest Digest #160, Volume #9 Sun, 28 Feb 99 14:13:03 EST
Contents:
Re: Quantum Computation and Cryptography (R. Knauer)
Re: Testing Algorithms (Somniac)
Re: Miller-Rabin prime test. Random bit size (Scott Fluhrer)
Re: is there any SRP/SSH/encrypted telnetd/encrypted ftpd SERVER (not client) for
Windows NT? ("D")
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From: [EMAIL PROTECTED] (R. Knauer)
Subject: Re: Quantum Computation and Cryptography
Date: Sun, 28 Feb 1999 15:06:06 GMT
Reply-To: [EMAIL PROTECTED]
On Sat, 27 Feb 1999 20:19:41 -0800, Anthony Stephen Szopa
<[EMAIL PROTECTED]> wrote:
>Can the quantum computer determine the truth from a lie? In other words, I
>have a message and add lots of leading and trailing bits of random noise.
>And interspersed throughout the message I also insert random noise.
>Then I encrypt the message. My recipient has the key that will not only
>decrypt the message but remove all the random noise as well.
>
>How will the quantum computer determine the correct intelligence communicated
>from what was essentially a message that lied?
>
>Quantum computers may be smart: like an idiot savant child.
I have no idea how to begin answering that question.
You might say that because quantum computers are based on actual
physical reality, they must reflect the inherent truth in physical
reality, but then they are indeterminant devices so it would seem
likely that they can return incorrect results, e.g., they could"lie"
or be unable to detect a lie.
>As far as good encryption is concerned, quantum computers pose no real
>threat.
Threat to what? Quantum algorithms exist to factor the product of two
large integers in polynomial time. That means that the RSA public key
cryptosystem is vulnerable. So are any other systems that rely on the
classically intractable problems like factoring large integers.
>The idea that by inputting an encrypted message into a black box quantum
>computer and that it will absolutely output the correct encrypted message is
>preposterous.
That's odd - it has already been demonstrated, and over a distance of
30km too. (Marand and Townsend, 1995). The original model was
demonstrated by Bennett and his coworkers at IBM.
There is more than one scheme for building a quantum computer. The
first one involved encoding the bits in the polarization of light. But
you can also encode the bits on the phase of the light.
>This is just more dogma from another stupid religion.
I heard no one mention anything about any "stupid religion". What
stupid religion are you referring to?
Or do you consider modern physics to be a form of stupid religion?
People who do not understand modern physics claim that physicists are
psychotic. To claim that they are practitioners of a "stupid religion"
is a new one.
Bob Knauer
"If you want to build a robust universe, one that will never go wrong, then
you don't want to build it like a clock, for the smallest bit of grit will
cause it to go awry. However, if things at the base are utterly random, nothing
can make them more disordered. Complete randomness at the heart of things is the
most stable situation imaginable - a divinely clever way to build a universe."
-- Heinz Pagels
------------------------------
From: Somniac <[EMAIL PROTECTED]>
Subject: Re: Testing Algorithms
Date: Sun, 28 Feb 1999 09:50:00 -1000
Herman Rubin wrote:
>
> In article <[EMAIL PROTECTED]>,
> Trevor Jackson, III <[EMAIL PROTECTED]> wrote:
> >fungus wrote:
>
> >> "Trevor Jackson, III" wrote:
>
> >> > There is no minimum energy per reversible computation. There is a
> >> > minimum energy per irreversible computation. Between these two true
> >> > statements lies lots of room for misunderstanding.
>
> >> *something* has to trigger a change of state...
>
> >Yes. There is no claim to perpetual motion. Every state change has to be
> >driven by some expenditure of energy. But, there is no limit on how small
> >that amout of energy can be when the computation is reversible. Thus, it
> >can be arbitrarily, ridiculously small. Efffectively zero even though not
> >actually zero.
>
> This is off-topic for this group, but it still needs addressing.
>
> The problem is NOT to produce state changes with extremely low
> energy; this is not difficult. It is to produce state changes
> which will not reverse spontaneously or from transient noise.
> A "permanent" magnet illustrates the situation; it has a large
> hysteresis loop, which means that most of the energy in changing
> its state goes off in heat, but this keeps it stable. Computer
> memory, and also the state of more accessible units, is like this;
> changeable, but not too easily so. The latter is what is needed
> to keep it from being lost.
> --
> This address is for information only. I do not claim that these views
> are those of the Statistics Department or of Purdue University.
> Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
> [EMAIL PROTECTED] Phone: (765)494-6054 FAX: (765)494-0558
Yes, true. And expand upon this wishful thinking about computing 2^256
answers without heating up the Earth by 99 degrees, consider the Carnot
Cycle using reversible adiabatic processes. No container has ever been
built which provides reversible adiabatic processes. Insulators are not
perfect, so some heat leaks out. Therefore, no one has ever built an
ideal Carnot engine. In addition, the intake temperature of a heat engine
must be lower than the exhast temperature.
In general, physical systems are "idealized" for mathematical teachings,
to illustrate a point for students. In reality, there have always been
frictions and losses for computing machines and any machines. Even
superconductors require work to get the helium, to make the generators,
to assemble the batteries.
Even gravity has costs so that its conservative potential effects have a
cost: make your own planet, then conserve energy during future idealized
experiments on an isolated partical (which has never existed in the
past). Or use our planet and pretend that it is absolutely free of cost.
It takes a force outside of an idealized experimental apparatus to show
for students, an "isolated" reversible process.
To make 2^256 calculations, there is not present device which can
succeed. Future developments cannot relied upon to create perpetual
motion computers that have reversible adders, nand gates, and memory. The
past shows that most inventions failed to become practical.
------------------------------
From: Scott Fluhrer <[EMAIL PROTECTED]>
Subject: Re: Miller-Rabin prime test. Random bit size
Date: Sun, 28 Feb 1999 18:32:22 GMT
In article <ZS9C2.1043$[EMAIL PROTECTED]>,
"Michael Scott" <[EMAIL PROTECTED]> wrote:
>
>I agree. But be careful. As I recall from some experiments I once did, a
>base of 2 misses all primes of the form 2^n-1.
^^^^^^
Huh? If we are talking about the Miller-Rabin test, then given a prime,
if always outputs 'probable prime' for all bases [1]. I don't see how
it could 'miss' a prime of any form. And, if you meant composite, a
quick check shows that 2**14 == 4 mod 15 and 2**62 == 4 mod 63, so it
doesn't 'miss' the first two composites 15 and 63 [2].
What did you mean?
> And such primes may be of
>interest in for example Elliptic Curve based systems.
Actually, if you are interested in primes of the form 2^n-1, there's a
site on the Web ( http://www.utm.edu/research/primes/mersenne.shtml#known )
that lists all such primes (Mersenne primes) to well over 2^1000000. If
you really want primes of that form, I suggest you look there rather than
trying to find your own.
[1] Note to pedants: unless, of course, the base is a multiple of the prime
in question.
[2] If a base is a liar for a given composite, then that composite must be
a pseudoprime to that base, and the above shows that 15 and 63 are not
pseudoprimes to base 2.
--
poncho
------------------------------
From: "D" <[EMAIL PROTECTED]>
Subject: Re: is there any SRP/SSH/encrypted telnetd/encrypted ftpd SERVER (not client)
for Windows NT?
Date: Sun, 28 Feb 1999 13:36:21 -0500
I suggest getting yourself a UNIX box with secure services and hooking it up
to the NT Server.
------------------------------
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