Re: OTP's [was: Re: Help: Randomizing a List of Numbers]

From: Arthur J. O'Dwyer (ajo_at_nospam.andrew.cmu.edu)
Date: 07/22/04 

Date: Thu, 22 Jul 2004 14:13:37 -0400 (EDT)

On Thu, 22 Jul 2004, Bill Emerson wrote:
>
> In sci.crypt, Tom St Denis wrote:
> > I strongly suggest you curb your fascination with OTPs. They might seem
> > "all cool and all" but they have zero practical value. You might as well
> > start in on learning what people have done instead [e.g. public key crypto
> > for instance].
>
> Almost everything else I have read tells me that your advice above is
> stupid and ignorant.

  Not really. I don't think you're paying attention to the Big Picture
here. OTPs require a secure channel to transmit huge chunks of key
data, in private, to every person in the world that you will ever want
to talk to. Let's say you want to communicate privately with 100
different people in your lifetime (probably an underestimate). And
you want to send each of them 2GB of data (probably an overestimate).
So you'll need a secure channel capable of sending 200GB of key data.
Multiply that by the one billion people in the world who might be
interested in doing the same thing (probably an overestimate), and
that's one heck of a business opportunity for FedEx.

  As Rob Warnock wrote in response to my post, if you want a higher
level of security, you'll want to send about three times that much
key data. Of which maybe 1% will get lost, and so you'll have to
resend new data (not the old data again, since Eve might be listening).
(This will happen about 3% of the time.)

  That's a lot of CDs. And a lot of computers doing nothing but
picking random numbers out of a hat, when they /could/ be doing useful
things, like downloading movies or looking for big Mersenne primes. :)

  Now, what Tom's suggesting is that OTPs don't actually add any
security over modern methods, such as public-key encryption; and
in addition, public-key encryption requires that you send, not
606GB of key data, but about 1KB, right when you start using it.
And the security (real-world) is about the same! So don't bother
with "serious" OTP software, when you could be exercising your brain
on modern crypto that's a lot less computer-intensive.

-Arthur

Quantcast